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• 1955 Chevrolet Vehicles
• 1956 Chevrolet Vehicles
• 1957 Chevrolet Vehicles

SECTION 6

ENGINE ASSEMBLY

CONTENTS OF THIS SECTION

For 1956 one six cylinder engine is provided for all passenger models and types of transmissions. The new Blue Flame Engine has 140 horsepower with a displacement of 235.5 cubic inches, a 3 9/16", bore, 3 15/16" stroke and 8:1 compression ratio. The engine develops 210 ft. lbs. of torque at 2400 RPM. All six cylinder engines are equipped with hydraulic valve lifters and high lift camshafts to provide better performance and facilitate maintenance problems.

The cylinder head assembly, as installed on the engine, includes the valve guides, valves, valve springs, rocker arm and shaft assemblies, spark plugs, temperature indicator fitting, water outlet, exhaust and intake manifolds and other assembling parts.

The carburetor and air cleaner assembly is bolted to the top of the intake manifold. The rocker arm cover is attached to the top of the cylinder head by four screws and encloses the valve mechanism.

The cylinder block and crankcase assembly is the major section of the engine as it is fitted with the camshaft, crankshaft, timing gear plate, timing gears, pistons, piston rings, piston pins, connecting rods and miscellaneous parts. In addition to the above parts which are part of a cylinder block assembly, the following units are attached to this assembly when in the vehicle-water pumps oil pump, distributor, starter, generator, flywheel, clutch and transmission or Powerglide transmission, harmonic balancer, fuel pump and other miscellaneous parts.

A "V" type fan belt operating from a combined harmonic balancer and pulley on the front of the crankshaft drives the generator, water pump and fan.

The distributor, mounted on the right side of the engine, is gear driven from the camshaft. The oil pump connects to the lower end of the distributor shaft and is driven at distributor speed. The fuel pump mounts on the right side of the engine and is operated by a special cam on the camshaft.

Pistons, of cast alloy aluminum, are cam ground to provide slightly greater diameter at right angles to the piston pin. Pistons have three piston ring grooves above the piston pin bosses. The piston pin bosses are bored 5/64" off-center, a type of construction that reduces the severity of piston slap such as might be encountered in cold engines.

One oil control ring and two compression rings are used on each piston. The oil control ring is composed of four units, an upper rail, a lower rail, a separator and an expander of zig zag type construction. All compression rings are of t e deep section twist type.

The exhaust valves on both models are aldipped on the seat portion to insure long valve life. All valves are of solid alloy steel.

Camshaft bearings are steel backed and babbitt lined, providing uniform expansion and long life. The bearings are installed in the cylinder block and finish bored for precise alignment.

Main bearings are precision interchangeable, thin wall babbitt type with dual advantages of longer life and simplified installation. Babbitt thickness is .003" to .007". This type of bearing gives increased bearing life and at the same time provides satisfactory embedability, or the ability of the babbitt to absorb foreign particles and so prevent scoring.

The precision interchangeability features of the bearings facilitate engine repair as well as engine assembly because the bearings are accurately machined to close tolerances and are ready for installation as received.

The crankshaft has four large bearing journals. It is heavily counterbalanced and weighs approximately 78 pounds, contributing to Chevrolet's smooth engine performance.

The four bearing cast iron camshaft is designed to provide accurate, quiet valve action and hold the valves open long enough to provide complete discharge of the exhaust gases and allow entry of a full charge of fuel mixture. The cams have a wear resisting treatment, which combined with off-center lifters, provide unusually long life and quiet operation, The camshaft is a hi-lift cam design in the Powerglide model.

Connecting rods are of large section, drop forged "I" beam construction for rigidity and strength. The upper end is fitted with a clamp bolt for securely attaching the rod to the piston pin. All connecting rod bearings are of the precision interchangeable insert type.

On standard transmission vehicles, a heavy cast iron flywheel bolts to a flange at the rear end of the crankshaft and a steel ring gear is shrunk on the outer diameter of the flywheel. On Powerglide transmission vehicles, a reinforced steel stamping with a welded ring gear is used. The starting motor drive pinion engages this ring gear when cranking the engine. Flywheel and crankshaft are accurately balanced to minimize engine vibration and the rear flywheel face on standard shift models is accurately machined for clutch mounting.

The front end of the crankshaft is fitted with a harmonic balancer. This balancer consists of a hub pressed onto the crankshaft and a small inertia weight riveted to the hub, interspaced by two rubber gromments. This rubber mounted weight is tuned to resist quick changes in crankshaft speed caused by the power impulses, and thereby dampens out or absorbs crankshaft vibration.

The same cylinder head is used on both engines and is designed to provide 7.5:1 compression ratio. Large water passages in the head provide adequate coolant capacity for efficient engine operation. The valve rocker cover attachment is provided at the gasket ledge through four screws, located midway between the center and/or front and rear of the cylinder head. This attachment provides excellent gasket sealing and valve operating noise suppression.

The intake manifolds are circular in cross section and are mounted to the engine with the main passage parallel to the ground.

The exhaust manifolds are designed to reduce back pressure to a minimum. Located on the inside of the exhaust manifold is the thermostatically operated heat control valve. This valve directs the hot exhaust gases against the center of the intake manifold when the engine is cold as shown at the left of Figure 2. As the engine warms up and engine speed increases, the thermostatic spring closes the valve and directs the exhaust gases away from the intake manifold as shown at the right of Figure 2. This thermostatic control results in the proper temperature of the incoming gases under all operating conditions.

A full pressure lubrication system is used on all engines. A gear driven oil pump maintains 35 psi pressure lubrication; it is equipped with a spring loaded by-pass valve to control maximum pressure at high speeds and when engine oil is cold and sluggish during cold weather starting. The engine pressure oil system is designed to provide positive lubrication of all moving parts ( fig. 3). Full pressure lubrication to the main and camshaft bearings is provided by oil flow from the oil pan through the floating pump screen to the oil pump to a block fitting and then to the oil gallery. From the oil gallery the oil passes through drilled passages in the main bearing support webs of the cylinder block to the four main bearings. The oil then passes through grooves in the bearings to passages drilled in the other side of the cylinder block webs and on to the camshaft bearings. The crankshaft also contains drilled oil passages connecting the main bearing journals with the crank-pins which provide positive pressure lubrication for the connecting rod bearings.

Timing gear lubrication is supplied by conducting oil through a milled slot in the rear surface of the engine front plate from the front camshaft bearing to a nozzle extending out from the front and so aimed that an oil stream effectively lubricates the timing gears.

Pistons and cylinder walls are lubricated by the oil spray thrown out through spurt holes in the connecting rods and bearings. Piston pin lubrication is maintained through two drilled passages in the top surface of the recessed piston pin bosses.

Lubrication of the valve mechanism is supplied by a drilled passage from the rear camshaft bearing to the pipe located under the push rod cover to a fitting at the top of the cylinder block. The oil then flows through a passage drilled in the cylinder block and head to the valve mechanism oil connector pipe between the two hollow rocker arm shafts, then distributed to all rocker arm bearings. A bleeder hole in each rocker arm supplies oil for lubrication of the valve stems and push rod sockets.

Lubrication control of the inlet and exhaust valve stems is provided by an oil seal. A synthetic rubber seal is assembled between the valve stem and the valve spring cap. An extra groove is provided on the valve stem to accommodate this rubber seal. Both seal and cap are interchangeable between intake and exhaust valves. Valve stem tips are hardened and finished to reduce wear and noise from contact with the rocker arms.

The engines used in models equipped with Powerglide transmission have hydraulic valve lifters that provide a means of automatically maintaining zero valve lash or tappet clearance at all times.

A direct oil feed is maintained to the lifters at all times through a 9/16" oil gallery which runs the full length of the engine. This gallery goes through the center of each valve lifter bore and intersects an oil passage drilled in the block from the rear camshaft bearing. Whenever lash tends to be present, the plunger spring expands, pushing the plunger until solid contact is made with the push rod and linkage. This creates a difference in oil pressure on either side of the ball check valve, the lower pressure being below the plunger. The higher pressure above then forces the oil to flow to the chamber below the plunger until the pressure is equalized. When the lifter is raised by the cam, the oil pressure is increased below the plunger, and forces the ball check valve against its seat. The oil space then becomes a hydraulic ram and is effectively a solid link in the mechanism to lift the valve. There is a certain controlled amount of oil leakage between the plunger and lifter body while the engine valve is open. This controlled clearance is necessary to the operation of the valve train. It permits positive valve closing even though the valve train effectively changes length during warm-up and operation.

Care, Maintenance and Adjustments

Engine or under hood maintenance is divided into three categories, routine inspection, periodic maintenance and tune-up. Each category serves to insure the maximum in performance, economy and long life built in to the Chevrolet engines.

ROUTINE INSPECTION

The routine inspection operations are those items which should be checked at regular intervals, determined by the service condition of the vehicle and varying from daily to semi-monthly. The engine oil level should be maintained between the "Full" and "Add" marks on the dipstick. The battery electrolyte level should be maintained at the bottom of the split rings in the battery filler openings, by the addition of distilled or demineralized water. The cooling system fluid level should be maintained one inch below the bottom of the filler neck on the radiators with a cold cooling system or at the bottom of the filler neck when the system is warm. These three checks are important to prevent damage to the battery and engine and should be made as frequently as driving conditions demand.

The periodic maintenance includes those items requiring service at the regular 1000 mile lubrication operations. As called out in the Lubrication Section of this manual, these items are the starter solenoid, crankcase breather, generator and distributor. In addition, an engine crankcase oil change and air cleaner element cleaning is recommended every 2000 to 3000 miles as discussed in the Lubrication Section of this manual.

Engine Tune-Up

One of the most important duties to perform on modern high compression engines is proper engine tune-up. This operation more than any other determines whether or not the vehicle will produce the maximum amount of performance with the greatest amount of economy. Only by performing these operations and staying within limits, clearances and specifications, is it possible to obtain the performance and economy built into the Chevrolet engine.

Tune-up operations should follow a definite procedure. A process of elimination by checking each individual component one by one is costly and time consuming. A fast, high-quality tune-up can be performed, using a group of test instruments designed specifically for tune-up work. By combining tune-up operations with testing operations, only the necessary items need be serviced and top performance will be assured with a minimum of time and cost.

Before making any checks on an engine, it should be run for several minutes and allowed to warm up and normalize. This assures proper lubricant vicosity at each engine component and that engine components will be at their operating temperature and size.

In each of the following tests and operations, a visual inspection should always be made for unusual or out-of-line conditions.

Cranking Voltage Test

The cranking voltage test checks the starting mechanism and circuit as well as the ignition primary circuit to the coil and will check to see that the coil resistor is shorted out during cranking.

1. Connect a voltmeter of approximately 16 volts capacity with the positive lead to the positive or battery terminal of the ignition coil and the negative lead to a good ground.
2. Remove coil wire from distributor cap.
3. Turn ignition switch to on position, note meter reading and then turn switch to start position. Check engine for 15 seconds and read voltmeter while still cranking.

With the switch in the ON position, the meter should indicate 5 to 7 volts. If it does not, refer to the Engine Electrical Section of this manual for further checks. With the switch in the START position, the meter should read 9.0 volts or better with a good rate of cranking speed. If the reading is below 9.0 volts or the engine cranks slowly, further tests must be made to determine the cause. The Engine Electrical Section of this manual outlines the battery testing, starter circuit testing and ignition primary circuit testing procedures.

Battery Hydrometer Test

In normal operation, a charging system in good condition should maintain the battery in at least a 3/4 charge condition. A hydrometer test should show a specific gravity of at least 1.215 or better and a maximum variation between cells of 0.025 gravity points. If either of these two specifications are not met, the battery and charging system should be thoroughly checked and tested as outlined in the Engine Electrical Section of this manual.

After the hydrometer check, the electrolyte level should be brought up to the bottom of the split-rings in the filler openings. If there is evidence of acid, dirt or resultant corrosion on the top of the battery, the top should be cleaned with ammonia or soda water and flushed with water. Exercise care not to get solution in the filler holes through vent holes. If the terminals show corrosion, they should be removed and the terminal and posts thoroughly cleaned. The posts and terminals should be completely coated with petrolatum and then reassembled and tightened securely.

Compression

The compression of each cylinder should be checked, because an engine with uneven compression cannot be tuned successfully to give peak performance.

1. Remove any foreign matter from around the spark plugs, and then loosen them about one turn to break free any accumulation of carbon.
2. Start engine and accelerate to 1000 RPM to blow out the carbon. (Starting and accelerating the engine after the plugs are loosened is extremely important in preventing false compression readings due to chips of carbon being lodged under the valves.)
3. Stop engine and remove spark plugs, placing them in order that they were removed.
4. Block throttle in wide open position.
5. Insert compression tester in a spark plug hole.
6. Crank engine with the starting motor until the cylinder being tested passes through four compression strokes.
7. Repeat this test on all cylinders and record the compression reading of each cylinder.
8. Compression on all cylinders should be 130 pounds or better and all cylinders should read alike within 10 pounds for satisfactory engine performance.

Should a low compression reading be obtained on two adjacent cylinders, it indicates the possibility of a leak from one cylinder to the other, usually caused by a leak at the cylinder lead gasket. If the compression readings are low, or vary widely, the cause of the trouble may be determined by injecting a liberal amount of engine oil on top of the pistons of the low reading cylinders. Crank the engine over several times, then take the second compression test. If there is practically no difference in the readings when compared with the first test, it indicates sticky or poorly seating valves. However, if the compression on the low reading cylinders is higher and about uniform with the other cylinders, it indicates compression loss past the pistons and rings. The cause of low or uneven compression should be corrected before proceeding with an engine tune-up.

Spark Plugs

Spark plug life is governed to a large extent by operating conditions. To insure peak performance, spark plugs should be checked and tested frequently and replacement of spark plugs should be made as necessary.

The spark plugs used as standard equipment on all Chevrolet Passenger Car Engines are AC 44-5. If plug fouling is being experienced in a vehicle because of continuous low speed operation, AC 46-5 plugs are available to combat this situation. If excessive electrode wear is experienced in a vehicle because of continuous heavy duty or high speed operation, AC 43-5 COM plugs are available for better spark plug life.

Worn and dirty plugs may give satisfactory operation at idling speed, but under operating conditions they frequently fail. Faulty plugs are evident in a number of ways such as, wasting gas(in extreme cases one gallon in every ten), loss of speed and power, hard starting and general poor engine performance.

Spark plug failure, in addition to normal wear, may be due to dirty or leaded plugs, excessive gap or broken insulator.

Dirty or leaded plugs may be evident by black carbon deposits, or red, brown, yellow or blistered oxide deposits on the plugs. The black deposits are usually the result of slow speed driving and short runs where sufficient engine operating temperature is seldom reached. Worn pistons, rings, faulty ignition, over-rich carbonization and spark plugs which are too "cold" will also result in carbon deposits. These deposits, a consequence of the use of leaded fuel, usually result in spark plug failure under severe operating conditions. The oxides have no adverse effect on plug operation as long as they remain in a powdery state. But, under high speed or hard pull, the powder oxide deposits melt and form a heavy glaze coating on the insulator which, when hot, acts as a good electrical conductor, allowing current to follow the deposits and short out the plug.

Excessive gap wear on plugs of low mileage, usually indicates the engine is operating at speeds or loads that are consistently greater than normal or that a plug which is too "hot" is being used. In addition, electrode wear may be the result of plug overheating, caused by combustion gases leaking past the threads and gaskets, due to insufficient compression of the spark plug gaskets, or dirt under the gasket seat. Too-lean carburetion will also result in excessive electrode wear.

Broken insulators are usually the result of improper installation or carelessness when regapping the plug. Broken upper insulators usually resulting from a poor fitting wrench or an outside blow. The cracked insulator may not make itself evident immediately, but will as soon as oil or moisture penetrates the fracture. The fracture is usually just below the crimped part of the shell and may not be visible. Broken lower insulators usually result from carelessness when regapping and generally are visible. In fairly rare instances, this type of a break may result from the plug operating too "hot" such as encountered in sustained periods of high speed operation or under extremely heavy loads. When regapping a spark plug, to avoid lower insulator breakage, always make the gap adjustment by bending the ground or side electrode. Never bend the center wire. Spark plugs with broken insulators should always be replaced.

Clean the spark plugs thoroughly, using an abrasive-type cleaner. If the porcelains are badly glazed or blistered, the spark plugs should be replaced. All spark plugs must be of the same make and number or heat range. Use a round feeler gauge to adjust the spark plug gaps to .035".

CAUTION: In adjusting the spark plug gap, never bend the center electrode -V which extends through the porcelain center. Always make adjustment by bending the ground or side electrode.

Install the spark plugs in the engine with new gaskets and tighten to 20-25 ft. lbs. torque. If torque wrench is not available, tighten plugs finger tight and 1/2 turn more. Plugs are of a 14 millimeter size and care must be exercised when installing or the gap setting may be changed.

Air Cleaner

1. Remove wing nut, cover and filter element.
2. Wash filter element thoroughly in cleaning solvent.
3. Let element dry and dip in engine oil and allow excess oil to drain.
4. Install element and cover and secure with wing nut.

NOTE: If oil bath air cleaner is used, see instructions under Engine-Fuel.

Manifold Heat Valve

The tension of the thermostatic spring is very important. When too tight, the heat will not be turned off the intake heat riser as the engine warms and speeds up, with the result that the incoming gases will be expanded several times greater than normal and it will be impossible to get a normal fuel charge into the cylinders. This condition will reduce power and maximum speed. Therefore, it is important that the thermostatic spring be wound up just enough to slip its outer end over the anchor pin (fig. 4) and no more. This is approximately 1/2 turn of the spring from its position when unhooked. Sometimes the heat control valve shaft seizes in the manifold; when this condition occurs the valve may stick in either the "heat on" or "heat off" position. If it sticks in the "heat on" position, it will result in poor engine performance, overheating and detonation. On the other hand, if it should stick in the "heat off" position, the heat will be turned off the intake heat riser at all times and result in poor performance, particularly while the engine is warming up and driving at lower speeds. On all engine tune-up jobs and also on complaints of poor performance, overheating and detonation, the operation and adjustment of the manifold heat control valve should be closely checked and any necessary corrections made.

1. Unhook the thermostat spring from its anchor pin and check the adjustment.
2. Proper adjustment requires only 1/2 turn of the spring from its unhooked position to slip it over the anchor pin. NOTE: Should this spring be distorted in any way it should be replaced.
3. Check valve shaft to make sure it is free in the manifold. If shaft is sticking, free it up with kerosene or alcohol containing a small amount of baking soda.

Ignition Distributor

1. Visually check the spark plug wires for damaged insulation and oil soaked condition.
2. Remove the distributor cap. Check the cap and distributor rotor for cracks or carbon tracks and burned or pitted contacts.
3. Check the distributor automatic advance mechanism by turning the distributor cam in a clockwise direction as far as possible, then release the cam and see if the springs return it to the retarded position. If the cam does not return readily, the distributor must be disassembled and the cause of the trouble corrected. See Engine Electrical Section for "Distributor Repair."
4. Check to see that the vacuum spark control operates freely by turning the distributor body counterclockwise and see that the spring returns it to the retarded position. Any stiffness in the operation of the vacuum spark control will affect the ignition timing.
5. Examine the distributor points. Dirty points should be cleaned with a clean point file. Normal point condition is an overall grey color. If a test instrument for checking resistance is available, check the point resistance. The criteria for point quality should be a combination of visual inspection and a resistance or voltage drop check. If the points are badly worn, pitted or misaligned, replacement is recommended. If, with the points closed and the ignition switch in the On position, there is less than a 0.125 volt drop across the points, the points may be considered satisfactory for further use. This check may be made with a sensitive voltmeter or one of the various point resistance meters available for this purpose. For point replacement procedure, see the Engine Electrical Section in this manual.
6. Check the contact point alignment and align the points if they have been cleaned or replaced. Align by bending the stationary point only.
7. Crank the engine until the cam follower is located between the cams. Hook the end of a distributor point scale over the movable point and pull steadily on the spring scale until the points just start to open. At this point the reading on the scale should be between 17-21 ounces. Adjust the tension by bending the breaker arm spring as required.
8. Crank the engine until the distributor point cam follower rests on the peak of the cam. Adjust the point gap to .016" for old points, .019" for new points, (fig. 5) using a feeler gauge or dial indicator. This operation must be performed very accurately because it affects point dwell or length of time the points remain closed in operation and, in turn, ignition coil performance.
9. If a dwell or cam angle meter is available, start the engine and check the dwell, which should be 26° to 33°. If the cam angle or dwell is outside the specified limits, recheck gap and check for defective or misaligned points, or worn distributor cam lobes. Proper point gap should produce a dwell angle within the specified limits.
10. If a dwell or cam angle meter is available, note dwell variation between idle and 1750 engine R.P.M. This should not exceed 3°. Excessive variation indicates wear in the distributor.

NOTE: Do not make dwell or cam angle readings above 1750 engine RPM

Ignition Timing

1. Set the octane selector at "0" on the scale (fig. 6) and attach a timing light to the No. 1 spark plug and spark plug wire, using an extension to make contact, and to a good ground. Start the engine and run it at idling speed with light aimed at flywheel housing opening.
2. Loosen distributor clamp and rotate distributor body until the steel ball in the flywheel lines up with the pointer on the flywheel housing.
3. Tighten distributor clamp screw and remove timing light.

Ignition Performance

If ignition performance test equipment is available, the ignition system performance should be tested in accordance with the equipment manufacturers procedures. If such equipment is not available, the ignition coil and distributor condenser should be checked on available equipment, and the ignition circuit wiring and terminals thoroughly inspected.

Carburetor

1. Inspect carburetor for loose body screws, damaged linkage, loose mounting, fuel leaks or excessive dirt accumulations.
2. Start and operate engine for a sufficient period of time for engine to reach normal operating temperature.
3. Set idling speed by adjusting stop screw on carburetor throttle lever, 450-500 RPM with Standard Transmission, 400-450 RPM with Powerglide Transmission in Drive range.
4. Turn idle screw gradually to right or left to give peak RPM and highest steady reading on vacuum gauge.
5. If engine idles too fast after this adjustment, readjust throttle stop screw until correct idle speed is obtained. Recheck idle mixture adjustment.

If any fault was found during visual inspection or it is impossible to obtain proper idle adjustment, remove carburetor from engine, disassemble, clean, inspect and reassemble carburetor as outlined under Engine-Fuel. Install carburetor and repeat idle adjustment.

Cooling System

1. Check all hoses and connections for evidence of leakage or decay. Make certain that the spring-type clamps are positioned squarely on the hoses and are over the pipe or casting that the hose is attached to.
2. Check the coolant level in the radiator, level with bottom of filler neck with a warm engine.
3. Check the fan belt condition and adjustment and adjust if necessary. Correct adjustment will produce 5/16" deflection with a light force applied midway between the fan pulley and generator pulley.

Operating Voltage

The operating voltage test serves as a check on the charging system in general. If the findings are not within limits, the entire charging system check should be made as outlined in the Engine Electrical Section of this manual before any adjustments are made.

1. Attach voltmeter leads to the battery terminal of the voltage regulator and ground.
2. Attach a tachometer to measure engine speed.
3. With a normalized engine, and regulator, start engine and run at 1750 RPM.
4. When voltmeter needle stabilizes, note reading. The reading should normally be 14.0 to 15.0 volts. The reading should be correlated with the battery hydrometer check and electrolyte level check if over-charging or under-charging is suspected. See the Engine Electrical Section of this manual for a more complete discussion on voltage regulator settings and charging system checks.

Road Test

After the completion of the tune-up, the vehicle should be road tested to check out the job and add insurance to the value of the tune-up.

With the engine warmed up and normalized, torque the cylinder head and manifold bolts as outlined under Cylinder Head Service Operations in this section. On models equipped with standard or overdrive transmissions, adjust the valves as outlined under Cylinder Head Service Operations in this section. Correct valve lash is .006" on intake valves, .013" on exhaust valves. Engines equipped with hydraulic valve lifters do not normally require valve adjustment on tune-up operations.

Solid Valve Lifters

Before adjusting the valve stem to rocker arm clearance, it is extremely important that the engine be thoroughly warmed up to normalize the expansion of all parts. This is very important because during the warm-up period, the valve clearances will change considerably. To adjust the valves during or before this warm-up period will produce clearances which will be far from correct after the engine reaches normal operating temperature.

Tests have shown that valve clearances will vary as much as .005" from a cold check through the normalizing range; consequently the engine should be run approximately 30 minutes to properly normalize all parts.

Covering the radiator will not materially hasten this normalizing process because even with the water temperature quickly raised, it does not change the rate at which the oil temperature increases or the engine parts become normalized.

The actual temperature of the oil is not as important as stabilizing the oil temperature. The expansion or contraction of the valves, rocker arm supports, push rods, cylinder head and cylinder block are relative to this oil temperature. Therefor, only after the oil temperature is stabilized, do these parts stop expanding and valve clearance changes cease to take place.

1. Remove rocker arm cover attaching screws, cover and gasket.
2. Normalize engine.
3. Tighten all manifold bolts, valve rocker shaft support bolts and cylinder head bolts. NOTE: Cylinder head bolts should be tightened to 90-95 ft. lbs. tension in the order shown (fig. 7), rocker shaft support bolts to 25-30 ft. lbs., manifold center clamp bolts to 15-20 ft. lbs. and manifold end clamp bolts to 25-30 ft. lbs.
4. Lubricate valve stems with engine oil to insure free movement of valves in their guides.
5. Adjust valve clearances on intake valves to .006" and on exhaust valves to .013".
6. Install rocker arm cover using a new gasket and check for oil leaks.

Hydraulic Valve Lifters

The hydraulic valve lifters used in all models and in all six cylinder engines for the first time, very seldom require attention. The lifters are extremely simple in design ( fig. 1), readjustments are not necessary and servicing of the lifters requires only that care and cleanliness be exercised in the handling of parts.

The easiest method for locating a noisy valve lifter is by use of a piece of garden hose approximately four feet in length. Place one end of the hose near the end of each intake and exhaust valve with the other end of the hose to the ear.

In this manner, the sound is localized making it easy to determine which lifter is at fault.

Another method is to place a finger on the face of the valve spring retainer. If the lifter is not functioning properly, a distinct shock will be felt when the valve returns to its seat.

The general types of valve lifter noise are as follows:

1. Hard Rapping Noise-Usually caused by the plunger becoming tight in the bore of the lifter body to such an extent that the return spring can no longer push the plunger back up to working position. Probable causes are:
   • Excessive varnish or carbon deposit causing abnormal stickiness.
   • Galling or "pick-up" between plunger and bore of lifter body, usually caused by an abrasive piece of dirt or metal wedging between plunger and lifter body.
2. Moderate Rapping Noise-Probable cause is:
   • Excessively high leakdown rate or leaky check valve seat.
3. General Noise throughout the Train This will, in almost all cases, be a definite indication of insufficient oil supply.
4. Intermittent Clicking Probable causes are:
   • A microscopic piece of dirt momentarily caught between ball seat and check valve ball.
   • In rare cases, the ball itself may be out-of-round or have a flat spot.

In most cases where noise exists in one or more lifters, all lifter units should be removed, cleaned in a solvent, reassembled, and reinstalled in the engine. If dirt, varnish, carbon, etc. is shown to exist in one unit, it more than likely exists in all the units.

In instances where parts are damaged, particularly the plunger or lifter body, the complete lifter unit should be replaced. However, in rare or emergency cases an Arkansas hard stone may be used to remove metal scratches or humps; and if after correcting, the plunger will operate freely in the lifter body, the parts may be thoroughly cleaned and the unit reassembled and reinstalled.

A few precautions to follow when servicing the valve lifters are:

1. Plungers are not interchangeable, they are a selective fit at the factory. Should a plunger or lifter body become damaged, it is necessary to replace the whole unit.
2. The plunger must be free in the lifter body. A simple test for this is to be sure the plunger will drop of its own weight in the body.
3. There must be no excessive leakdown and there must be no ball check valve leakage.

Removal

1. Remove rocker arm cover attaching screws and remove cover and gasket.
2. Disconnect spark plug wires and disconnect high tension wire from coil. Remove push rod cover attaching screws and remove cover and gasket.
3. Remove bolts and nuts which retain valve rocker arm assembly to cylinder head and remove rocker arm assembly.
4. Remove the twelve push rods and twelve valve lifters.

NOTE: Valve lifters and push rods should be placed in a rack in their proper sequence so they can be reinstalled in their same positions in the cylinder block.

Disassembly and Assembly

1. Hold plunger down with a push rod and using a small screwdriver or pointed awl, remove plunger retainer.
2. Remove push rod seat, plunger, ball check valve, ball retainer and spring. Figure 8 shows a layout of the parts.
3. Thoroughly clean all parts in cleaning solvent, then inspect them carefully. If any parts are damaged, the entire lifter assembly should be replaced.
4. To reassemble, invert the plunger and set the ball into hole in plunger and place the ball check valve retainer over the ball and on the plunger.
5. Place check valve retainer spring over retainer.
6. Assemble valve lifter body over the complete assembly being careful to line up the feed holes in the lifter body and plunger.
7. Turn assembly over and fill with SAE 10 oil, then insert end of tool J-4274 through ball seat hole in bottom of plunger and press down solid, at which point holes in lifter body and plunger will be aligned.
8. Insert pin which is part of J-4274 through both holes to hold plunger down against spring tension. Remove tool from top of lifter.
9. Fill assembly with SAE 10 oil, install push rod seat and spring retainer.
10. Press down on push rod seat and remove pin. The hydraulic lifter is now completely assembled, loaded with oil and ready for installation in the engine.

Installation

1. Install valve lifters in cylinder block.
2. Install push rods and valve rocker arm assembly, and install push rod cover and gasket.
3. Replace high tension wire to coil and connect spark plug wires.

Adjustment

Any time the rocker arm assemblies or valve lifters are removed from the engine it is necessary to make an initial adjustment for each valve lifter. This adjustment must be made when the lifter is on the base circle of the cam according to the following procedure.

1. Remove distributor cap and crank engine until distributor rotor points to number one (1) cylinder position with the breaker points open. In this position the piston in number one cylinder is at top center on compression stroke with both lifters on the base circle of the cam and both valves can then be adjusted.
2. Turn adjusting screw down until all lash is removed from lifter to valve. This can be determined by checking push rod side play at adjusting screw end while turning the adjusting screw. At the point where no side play of push rod can be felt, continue turning adjusting screw down 1 1/2 turns and tighten lock nut securely. This places the lifter plunger in center of its travel and no further adjustment is required.
3. Crank engine until the distributor is pointing to number five (5) cylinder position. Then adjust both valves for number five (5) cylinder in the manner described above.
4. The other valves may be adjusted by setting the engine with the distributor as described above. It should be noted that we are following the firing order of the engine which is 1, 5, 3, 6, 2, 4; therefore, both intake and exhaust valves for each cylinder should be adjusted in this order.

The condition of the cylinder head and valve mechanism, more than anything else, determines the power, performance and economy of a valvein-head engine. Extreme care should be exercised when conditioning the cylinder head and valves to maintain correct valve stem to guide clearance, correctly ground valves, valve seats of correct width and correct valve adjustment.

Removal and Disassembly

1. Drain radiator, raise hood, loosen air cleaner clamp, remove support bolts and remove air cleaner.
2. Remove cotter pin at lower end of throttle rod and disconnect rod from bell crank and disconnect throttle return spring.
3. Disconnect gas and vacuum lines from carburetor.
4. Remove gas and vacuum line retaining clip from water outlet.
5. Remove canscrews and clamps that attach manifold assembly to cylinder head and pull manifold assembly off the manifold studs. Remove intake manifold pilot sleeves.
6. Disconnect radiator hose from water outlet, remove outlet to cylinder head bolts and remove outlet and thermostat.
7. Remove rocker arm cover attaching screws and remove cover and gasket.
8. Disconnect wires and remove all spark plugs.
9. Remove high tension wire from coil, remove coil attaching screws and lay coil down out of the way.
10. Remove push rod cover attaching screws and remove cover and gasket.
11. Remove temperature indicator element from cylinder head.
12. Remove four bolts and two nuts which retain rocker arm assembly to cylinder head and remove rocker arm assembly.
13. Remove twelve push rods and twelve valve lifters. NOTE: Valve lifters and push rods should be placed in a rack in their proper sequence so they may be reinstalled in the same positions in the cylinder block at assembly.
14. Remove the cylinder head bolts, cylinder head and gasket.
15. Place cylinder head assembly on its side on a bench then, using Valve Lifter Tool KMO-642, compress valve spring and remove valve lock, seal, spring cup and spring. Repeat this operation on each valve (fig. 9).
16. Remove valves from cylinder head and keep them in their proper sequence for inspection and assembly.

Cleaning

1. Clean all carbon from combustion chambers and valve ports using Carbon Removing Brush KMO-7004.
2. Thoroughly clean the valve guides, using Valve Guide Cleaner KMO-122.
3. Clean all carbon from push rods and valve lifters, disassemble, clean and reassemble hydraulic valve lifters on models where used.
4. Clean valve stems and heads on a buffing wheel.
5. Clean carbon deposits from pistons and cylinders.
6. Wash all parts in cleaning solvent and dry them thoroughly.

Inspection

1. Inspect the cylinder head for cracks in the exhaust ports, combustion chambers, or external cracks to the water chamber.
2. Inspect the valves for burned heads, cracked faces or damaged stems.
3. Check fit of valve stems in their respective guides. This check may be made with a Last Word Indicator, so arranged that a side movement (crosswise to the head) of the valve stem will cause a direct indicator reading. The indicator stem must contact valve stem just above top of guide. With the valve head slightly (1/32") off its seat, move the valve stem from side to side and read the clearance. This should be .001" to .003" on intake valves, and on exhaust valves. By trying new valves in old guides, it can be determined whether the valves, guides or both should be replaced. NOTE: Excessive valve to guide clearance will cause lack of power, rough idling and noisy valves. Insufficient clearance will result in noisy and sticky functioning of the valve and disturb engine smoothness of operation.
4. Check valve spring tension with KMO-607 Valve Spring Tester (fig. 10). NOTE: On standard shift models, spring should be compressed to 1 1/2", at which height it should check 155 to 165 pounds. On Powerglide models, springs should be compressed to 1 29/64" at which height it should check 194 to 210 pounds. Weak springs affect power and economy and should be replaced if not within the above limits.
5. Check valve lifters for free fit in block. The end that contacts the camshaft should be smooth. If this surface is worn or rough the lifter should be replaced.
6. Check push rods for bent condition.

REPAIRS

Replace Valve Guides

1. Place the cylinder head on the table of an arbor press and press the old valve guides out using remover J-267 (fig. 11).
2. Press new precision exhaust (short) guides into the cylinder head using replacer J-5734.
3. Press new precision intake (long) guides into the cylinder head using replacer J-5599. NOTE: Replacer tools have stop collars for proper positioning of the guides.
4. The exhaust guides are installed in the head so they will extend 15/16" above the head and the intake guides extend 1" above the head (fig. 12).
5. Finish ream all guides with a .343" hand reamer.

Reseating Valve Seats

Reconditioning the valve seats is very important, because the seating of the valves must be perfect for the engine to deliver the power and performance built into it.

Another important factor is the cooling of the valve heads. Good contact between each valve and its seat in the head is imperative to insure that the heat in the valve head will be properly carried away.

Several different types of equipment are available for resealing valve seats; the recommendations of the manufacturer of the equipment being used should be carefully followed to attain proper results.

Valve reseater set KMO-105-B and J-4387 contains all necessary valve seat reconditioning equipment necessary for proper renewing of valve seats. Regardless of what type of equipment is used, however, it is essential that valve guides are free from carbon or dirt to insure proper centering of pilot in the guide.

1. Install proper expanding pilot in the valve guide and expand pilot by tightening nut.
2. Place roughing or forming cutter over pilot and just clean up the valve seat. Use a 31° cutter for intake and a 46° cutter for exhaust valve seats.
3. Remove roughing or forming cutter from pilot, install finishing cutter on pilot and cut just enough metal from the seat to provide a smooth finish.
4. Narrow down the valve seats to the proper width of 3/64" to 1/16" for the intake and 1/16" to 3/32" for the exhaust. NOTE: This operation is done by machining both port and top of valve seat.
5. A form cutter must be used to thin down the intake seats from the top. This cutter also machines the edge of the valve recess in the head smoothing this passage for the free flow of incoming gases.
6. Remove expanding pilot and clean head carefully to remove all chips from above operations. NOTE: Valve seats should be concentric to within .002" total indicator reading (fig. 13).

Refacing Valves

Valves that are pitted can be refaced to the proper angle, insuring correct relation between the head and stem on a valve refacing machine. Valve stems which show excessive wear, or valves that are warped excessively should be replaced. When a valve head which is warped excessively is refaced, a knife edge will be ground on part or all of the valve head due to the amount of metal that must be removed to completely reface. Knife edges lead to breakage, burning or pre-ignition due to heat localizing on this knife edge. If the edge of the valve head is less than 1/32" thick after grinding, replace the valve.

1. If necessary, dress the valve refacing machine grinding wheel to make sure it is smooth and true. Set the chuck at the 30 mark for grinding 30 intake valves. Set chuck at 45 mark for grinding exhaust valves (fig. 14).
2. Clamp the valve stem in the chuck of the machine.
3. Start the grinder and move the valve head out in line with the grinder wheel by moving the lever to the left.
4. Turn the feed screw until the valve head just contacts wheel. Move valve back and forth across the wheel and regulate the feed screw to provide light valve contact.
5. Continue grinding until the valve face is true and smooth all around valve. If this makes the valve head thin the valve must be replaced as the valve will overheat and burn.
6. Remove valve from chuck and place stem in "V" block. Feed valve squarely against grinding wheel to grind any pit from rocker arm end of stem. NOTE: Only the extreme end of the valve stem is hardened to resist wear. Do not grind end of stem excessively.
7. Make pencil marks about 1/4" apart across the valve face, place the valve in cylinder head and give the valve 1/2 turn in each direction while exerting firm pressure on face of valve.
8. Remove valve and check face carefully. If all pencil marks have not been removed at the point of contact with the valve seat, it will be necessary to repeat the refacing operation and again recheck for proper seating.
9. Grind and check the remaining valves in the same manner.

Rocker Arms and Shafts

Sludge and gum formation in the rocker arm shafts and rocker arm shafts restrict the normal flow of oil to the rocker arms and valves. Each time the rocker arm and shaft assemblies are removed they should be disassembled and thoroughly cleaned.

1. Remove the support bolts, hairpin locks, springs, rocker arms and supports.
2. Clean all sludge or gum formation from the inside and outside of the shafts and from valve rocker shaft tube.
3. Clean oil holes and passages in the shafts and rocker arms.
4. Clean the rocker arm shaft oil connector assembly.
5. Inspect the shafts for wear. Check the fit of rocker arms on the shafts and check the valve end of rocker arms for excessive wear. Replace all worn parts.
6. There are three each of four different type rocker arms used-right and left hand exhaust and right and left hand intake. They must be installed on the shafts in correct position. For identification each type rocker arm carries a different number stamped on the side.
7. The proper location of the rocker arms according to number are as follows:

 STANDARD SHIFT ENGINE

No. on Rocker Arm                  Type Rocker Arm                   For Cylinder No.
9                                  L.H. Exhaust                      1-3-5 Exhaust
0                                  R.H. Exhaust                      2-4-6 Exhaust
3                                  L.H  Intake                       2-4-6 Intake
4                                  R.H. Intake                       1-3-5 Intake

POWERGLIDE ENGINE

No. on Rocker Arm                  TYPE Rocker Arm                   For Cylinder No.
7                                  L.H. Exhaust                      1-3-5 Exhaust
8                                  R.H. Exhaust                      2-4-6 Exhaust
3                                  L.H  Intake                       2-4-6 Intake
4                                  R.H. Intake                       1-3-5 Intake

1. One end of each rocker arm shaft is plugged; the open end of each shaft must be toward the center.
2. Install the rocker arms, springs, supports, support bolts and locks in their correct position by referring t6 the above chart and Figure 15.

Assembly

1. Clean valves, valve seats, valve guides and cylinder head thoroughly.
2. Starting with No. 1 cylinder, place the exhaust valve in the port and place the valve spring and cap in position. Then using Valve Spring Compressor KMO-642, compress the spring and install the oil seal and valve keys (fig. 16). See that the seal is flat and not twisted in the valve stem groove and that the keys seat properly in the valve stem groove. NOTE: Place valve springs in position with the closed coil end toward the cylinder head.
3. Assemble the remaining valves, valve springs, spring caps, oil seals and valve keys in the cylinder head using tool KMO-642.
4. Check the installed height of each spring, measuring from the top of the spring to the spring seat on the cylinder head. If this is found in excess of 1 55/64", install valve spring seat shim, approximately 1/6" thick. At no time should the spring be shimmed to give an installed height of less than 1 51/64".

Installation

1. Thoroughly clean out cylinder head bolt holes in block and clean cylinder bolt threads. Place a new cylinder head gasket in position on the cylinder block following the instructions stamped on the gasket. This assures alignment of water passages and bolt holes in the block and head with openings in the gasket.
2. Place two cylinder head guide pins through the gasket and screw them into the cylinder block front and rear holes on the manifold side to hold the gasket in position and guide the cylinder head into place.
3. Place the cylinder head in position over the guide pins, and lower the head into position.
4. Oil threads of cylinder bolts and install cylinder head bolts finger tight. Remove guide pins and install two remaining bolts.
5. Tighten the cylinder head bolts a little at a time in the order shown in Figure 7. The final tightening should be to 90-95 ft. lbs.
6. Install 12 valve lifters in right side of block and drop the 12 valve push rods down through the openings in the cylinder head and seat them in the lifters.
7. Place the oil connector over open ends of the two rocker shaft assemblies, install rocker arm assembly retaining bolts in assembly and place shaft assembly on the cylinder head. Align oil return tube with drain hole in cylinder head.
8. Tighten retaining bolts evenly to 25-30 ft. lbs. torque. Figure 17 shows rocker arm and shaft assemblies correctly intalled on head.
9. Install temperature indicator fitting and tighten securely.
10. Install thermostat and thermostat housing using a new gasket and connect radiator hose.
11. Place coil in position and install attaching screws, tighten screws to 5-8 ft. lbs. torque.
12. Clean all spark plugs with abrasive type cleaner, inspect for damage and using a round feeler gauge, set the spark gap at .035".
13. Place new gaskets on plugs and install. Tighten to 20-25 ft. lbs. If torque wrench is not available, tighten finger tight and 1/2 turn more.
14. Connect spark plug wires to their respective terminals and the high tension wire to the coil.
15. Clean gasket flanges on cylinder head and manifold, and install new gaskets, intake manifold pilot sleeves, and the four cap screws with clamps loosely to hold gaskets in place. Position the manifold and slide it into place over the end studs and pilot sleeves, making sure it seats against the gaskets.
16. Install the two end cap screws with clamps and turn the center clamps into position against manifold. Tighten the center clamp bolts to 15-20 ft. lbs. torque and the two end clamp bolts to 25-30 ft. lbs. torque.
17. Connect lower end of throttle rod and install a new cotter pin.
18. Connect gas and vacuum lines to carburetor, and vacuum lines to manifold fitting.
19. Attach gas and vacuum line retaining clip to water outlet.
20. Fill cooling system and check for water leaks.
21. Clean air cleaner and install.
22. Roughly set all valve clearances to make sure that all valves have clearance.
23. Normalize engine and adjust valves as instructed under Care, Maintenance and Adjustments, Valve Adjustment.

Effective crankcase ventilation is provided on all engines by a road-draft tube type of system. A ventilator tube, leading from the crankcase, is exposed to the air moving underneath the vehicle. The shape and position of the end of the tube is such that a differential of pressure is created between the ends of the tube. Thus, in addition to providing a ready exhaust for any crankcase pressure due to vapor formation, heat expansion or piston blowby, a draft is created through the engine. The path of the draft is from a breather filter in the sealed valve rocker cover on top of the engine, through the valve train section of the engine to the crankcase to the ventilator tube. In this manner, crankcase vapors are drawn from the engine as they are formed, reducing the possibility of harmful acid or sludge formation in the lubricating oil.

The only service required for this system is the cleaning of the breather intake filter and road-draft tube.

The breather filter should be cleaned with a solvent every 2000 miles. After cleaning, oil the mesh with light engine oil.

The road-draft tube seldom requires service. Driving conditions determine the length of time required to build up a sludge formation in the tube. If there is evidence of crankcase pressure, such as leaking seals on the crankshaft above and beyond normal conditions, -the tube should be checked as a possible source of trouble. The tube should be removed from the vehicle for cleaning, which may be done with solvents or by burning out the sludge formation. This is a good precaution on high mileage engine overhauls.

Positive crankcase ventilating units are available as an option. Installation of this unit will serve:

1. To prevent entrance of dust or dirt into the crankcase on vehicles that are operated in dusty areas. Dust and dirt in the crankcase and oiling system will result in rapid wear of main and connecting rod bearings, piston rings, cylinder walls and other moving parts. NOTE: An oil bath air cleaner should also be used in dusty areas.
2. To provide adequately controlled crankcase ventilation on vehicles used continuously in slow speed, door to door delivery and similar type operations by effectively removing harmful vapors which contaminate the oil, also to prevent corrosion and sludge formation in the crankcase.

Operation

Positive crankcase ventilation is accomplished by utilizing the vacuum created in the intake manifold and the system features controlled circulation of clean air through the crankcase and valve chamber at all engine speeds and loads. Clean air is drawn into the engine from the carburetor air cleaner through a ventilation valve which regulates the amount of ventilation to meet changing operating conditions. To assure proper operation of positive crankcase ventilation system it is important that the crankcase oil level be correctly maintained and not over filled.

When the positive crankcase ventilation system is installed on a Chevrolet engine an extra quantity of air is permitted to enter the intake manifold below the carburetor. This may in some instances result in a leaner air-fuel ratio in the engine than is desirable. No change in carburetion should be made unless definite evidence of lean mixture is experienced. If this condition is experienced, one step rich main metering jet may be used in the carburetor.

Maintenance

The positive crankcase ventilation system will operate effectively as long as normal maintenance is applied. Due to the nature of the materials carried by the ventilating system, the valve and pipe are subject to fouling with sludge and carbon formation.

At regular intervals of 10,000 miles or less, depending on operating conditions, the metering valve, the pipe running from the valve to the intake manifold and manifold fitting should be removed from the engine, disassembled and cleaned thoroughly.

NOTE: Under cold weather operating conditions, when vehicles are operated at slow speeds with low engine temperatures, more rapid accumulations of harmful fumes may be present in the engine. Under these conditions of operation the valve and tube must be cleaned more frequently than specified above. However, no specific mileage recommendation can be made under these conditions. Frequency of cleaning must be dictated by experience.

Disassemble the valve (fig. 18) and clean the valve parts with any good solvent cleaner and the. v blow dry with compressed air. The jiggle pin, which floats in the center orifice of the valve, may be snapped out of position by pressing on the end of the pin so that the center orifice of the valve may be cleaned. The pin may then be snapped back into position.

When reassembling the valve parts, be sure to attach the spring on the valve by pushing the end coil over the tapered end of the valve, over the ridge and into the groove machined just under the head of the valve. This is very important. Unless the spring is properly assembled, the valve will not contact the valve seat squarely and will not close properly. Consequently, the engine will not idle properly due to the entrance of too much air into the intake manifold. If the spring has been stretched the same trouble may occur.

If improper action of the spring is suspected due to spring being distorted, bent or etched from corrosive action, the valve assembly should be replaced. Clean the steel ventilator connection tube and intake manifold connector with solvent and blow dry with compressed air.

Remove oil filler tube and inspect for sludge accumulation, if necessary burn clean, make sure all holes in baffle inside of oil filler tube are open. Inspect oil filler cap and gasket for sealing. If necessary replace gasket as ventilating system efficiency depends on a sealed cap at this point. Inspect for and correct any air leaks at valve rocker cover gasket, valve side cover gasket and ventilator connecting tube and fitting to prevent entrance of air.

A section drawing (figure 4) is shown in order to familiarize servicemen with the air flow through the positive ventilation system. The system is simple yet very effective. The only moving part of the system is the operation of the ventilation valve which is controlled by engine vacuum.

Improper functioning of the ventilation valve may cause erratic operation of the engine. This condition may show up as any of the following troubles.

1. Engine stalls frequently after slow or quick stops. After restart of engine, engine runs rough, with typical lean idle fuel mixture.
2. Engine loss of power and surging at speeds above idle.
3. Considerable amount black smoke at tailpipe, engine has typical rich rolling idle.
4. Idle rpm speed fluctuates but does not stall. Engine does not stall.

Removal

1. Raise front of vehicle and place on stand jacks.
2. Remove oil pan drain plug and drain crankcase oil.
3. Disconnect steering idler arm bracket from right hand frame side rail and drop for clearance.
4. Remove oil pan retaining bolts and screws and remove oil pan. NOTE: Crankshaft may have to be repositioned to allow clearance at front cross member.

Installation

1. Thoroughly clean all gasket sealing surfaces.
2. Install pan side gaskets on cylinder block, using grease as a retainer.
3. Install oil pan end gaskets in grooves in front and rear main bearing caps.
4. Reverse the removal procedure to complete the installation. Corner bolts should be tightened to 12 1/2 to 15 ft. lbs., and side rail screws to 6-71/2 ft. lbs.

The oil pump (fig. 19) consists of two gears and a pressure relief valve enclosed in a two-piece housing and driven from the distributor drive shaft which in turn is driven by a helical gear on the camshaft.

The pump cover is equipped with the pressure regulator valve that limits oil pressure to approximately 35 psi.

The pump intake is of the floating type. It floats on the crankcase oil level, picking up only the cleanest oil in the sump. A mesh screen filters out small particles of dirt and sludge which may be present. In the event that the screen becomes clogged, a valve in the center of the float will allow the pump to pick up oil, by-passing the screen.

Inasmuch as the oil pump is serviced on an exchange basis, no repair operations other than disassembly and inspection operations are covered in this manual.

Removal and Disassembly

1. Remove oil pan.
2. Disconnect oil pump to block oil line at the block.
3. Remove oil pump retaining sleeve lock screw and remove oil pump and pump to block oil line.
4. Remove pressure oil line from pump and remove pump cover attaching screws, cover, gasket, idler gear and drive gear and shaft.
5. Remove regulator valve pin and valve parts.
6. Remove floating intake screen from pipe by bending tang on float travel control and sliding float assembly off pipe. CAUTION: Do not disturb pick-up pipe. This pipe is located at assembly and controls controls level.
7. Wash all parts in cleaning solvent and dry by using compressed air, if available.

Inspection

Should any of the following conditions be found during inspection operations, it is advisable to replace pump assembly.

1. Inspect pump body for cracks or excessive wear.
2. Inspect oil pump gears for excessive wear or damage.
3. Check shaft for looseness in the housing.
4. Check inside of cover for wear that would permit oil to leak past the ends of gear.
5. Check the oil pick-up screen for damage to screen, by-pass valve or body. Check for oil in the air chamber.
6. Check pressure regulator valve plunger for fit in cover.

Assembly and Installation

1. Should it be necessary to replace the oil pump pipe to case fitting, caution should be exercised. The fitting should be installed finger tight plus one turn to avoid cracking the block.
2. Place drive gear and shaft in pump body.
3. Install idler gear so that smooth side of gear will be toward the cover.
4. Install a new GENUINE Chevrolet gasket to assure correct end clearance of the gears.
5. Install cover and attaching screws. Tighten screws securely and check to see that shaft turns freely.
6. Install regulator valve plunger, spring retainer and pin.
7. Install oil line to pump body loosely.
8. Install pick-up screen on pipe and bend float travel control tang back in place.
9. Place oil pump in block fitting, aligning oil lines and install oil pump retaining sleeve lock screw and tighten it securely. NOTE: Make sure that tapered end of lock screw draws down into hole in oil pump body. Tighten lock nut securely.
10. Tighten oil pump to block oil line connector nuts securely. CAUTION: Make sure oil lines are property fitted so as to eliminate the possibility of shaft seizure when tightened.
11. Install oil pan.

Removal

1. Drain radiator and disconnect upper and lower radiator hoses. On Powerglide models, remove oil cooler lines.
2. Remove radiator core to radiator core support bolts and remove radiator core. Note number of spacer shims removed.
3. Remove fan belt.
4. Install Harmonic Balancer Puller J-1287-B to harmonic balancer and turn puller screw to remove balancer and pulley assembly (fig. 20).
5. Remove oil pan.
6. Remove timing gear cover attaching screws and two bolts that are installed from the back through the front main bearing cap and remove cover and gasket.

Repairs

Timing Gear Cover Oil Seal-Replace

1. Pry old seal out of cover from the front with a large screwdriver.
2. Install new seal so that open end of the seal is toward the inside of cover and drive it into position with Oil Seal Driver J-995 (fig. 21).

Installation

1. Make certain that cover mounting face and cylinder block front end plate face are clean.
2. Install Timing Gear Cover Centering Gauge J-966 over end of crankshaft.
3. Coat the oil seal with light grease and using a new cover gasket install cover and gasket over centering gauge (fig. 22).
4. Install cover screws and two bolts through bearing cap and tighten 6-7 1/2 foot pounds torque. Remove centering gauge. NOTE: It is important that the centering gauge be used to align the timing gear cover so that the harmonic balancer installation will not damage the seal and to provide uniform seal tension on the hub of the balancer.
5. Install new oil pan gaskets and end corks. Carefully place the oil pan in position and tighten pan bolts securely. NOTE: Tighten oil pan corner bolts to 12 1/2 -15 foot pounds. Tighten flange bolts to 6-7 1/2 foot pounds.
6. Install relay rod idler arm bracket to frame side rail bolts and tighten securely.
7. Remove puller screw from harmonic balancer. Install two 3/8"-16 x 1" capscrews in balancer to support wheel portion during installation.
8. Position balancer on crankshaft so that keyway aligns with key in crankshaft and drive balancer onto shaft until it bottoms against crankshaft gear, using a heavy hammer and a long bar through the grille. Use care to obtain a straight installation. Remove two 3/8"-16 bolts previously installed.
9. Adjust the fan belt to give 5/16" deflection midway between pulleys.
10. Replace radiator core, spacer shims as required, and attaching bolts and tighten securely.
11. Replace upper and lower radiator hoses and refill cooling system.

Front and rear engine mountings are of the non-adjustable type. Because of this, service is seldom required. Broken or deteriorated mounts should be replaced immediately because of the added strain thrown on other mounts and drive line components.

Front Mounts-Replace

1. Remove top and bottom stud nuts and remove washer and cushion between each nut and the cross member or engine bracket.
2. Raise front of engine and remove studs with cushions, washers and retainers. CAUTION: Raise only for enough for clearance. Check for interference between rocker cover and body.
3. Replace necessary cushions (fig. 23).
4. On each end of studs, install washer, cushion with step and retainer.
5. Install stud and cushion assemblies in front cross member and lower engine into place.
6. Install cushion and washer over each end of each stud, install nut and tighten securely.

Rear Mounts-Replace

1. Support engine weight to relieve rear mounts.
2. Remove mount attaching bolts from frame outrigger and flywheel housing and remove mount.
3. Install new mount and bolts.
4. Remove engine support.
5. Tighten bolts securely with normal engine weight resting on mounts.

The dowel in the upper half of the precision main bearing has been discontinued for 1956. A tang is provided at one of the butting edges of the new upper bearing. This tang, which registers with a slot in the cylinder block and locates the upper bearing, also butts against the bearing cap to prevent rotation of the bearing. The adjustment shims formerly used between the bearing cap and cylinder block have also been discontinued.

Whenever main bearings are checked and excessive clearances found, new bearings should be installed.

REAR MAIN BEARING OIL SEAL - REPLACE

Sealing at the crankshaft rear bearing is made very effective due to machining the rear bearing cap and cylinder block to receive a wick type seal (fig. 24).

To install a new wick seal in the rear main bearing cap proceed as outlined below.

1. Remove rear bearing cap.
2. Remove old seal from groove and make sure groove is clean.
3. Insert new seal in groove with the fingers.
4. Using a rounded tool, roll the seal into the groove. NOTE: When rolling the seal start at one end and roll it to the center of the groove. Then starting from the other end, again roll toward the center (fig. 25).
5. Cut the small portion of the seal that protrudes from the groove flush with the surface of the bearing cap. NOTE: To prevent possibility of pulling seal out of groove a round block of wood the same diameter as the crankshaft flange may be used to hold packing firmly in place while the ends are being cut off.
6. If it should be necessary to replace the upper half of the seal, it will be necessary to remove the engine from the chassis and remove the crankshaft as outlined under Major Service Operations in this section.
7. Replace cap and adjust bearing.

Engine Removal

1. Drain cooling system, crankcase and transmission.
2. Scribe alignment marks on hood around hood hinges and remove hood from hinges.
3. Disconnect R.H. headlamp, parking lamp, and horn wires and remove wires from radiator core support brace.
4. Remove both horns.
5. Remove radiator hoses and heater hoses on models so equipped. On Powerglide, remove and plug oil cooler lines.
6. Remove radiator core support to fender bolts, core support to fender side baffle bolts and core support to front cross-member bolts. Remove radiator core and core support.
7. Remove battery, battery support and battery cables.
8. Disconnect starter and generator wires, engine to body ground strap, oil pressure indicator wire at switch on block and coil primary lead at coil.
9. Remove windshield wiper motor. Remove temperature indicator element from cylinder head.
10. Remove air cleaner.
11. Disconnect gasoline feed pipe from fuel pump and disconnect vacuum lines from intake manifold.
12. Remove exhaust pipe to manifold bolts.
13. Disconnect carburetor control rod from dash panel bell crank.
14. Remove transmission control rods.
15. Remove clutch control bell crank and control rods on conventional transmission models. On overdrive models, disconnect overdrive wires and cables. On Powerglide models, remove oil filler tube and plug opening.
16. Disconnect speedometer cable at transmission.
17. Split rear universal joint. Remove propeller shaft.
18. Remove rocker arm cover and install lifting hooks from Kit J-4536 in cylinder head bolt holes.
19. Raise engine slightly and remove all four engine mounts. Remove the engine and transmission from the vehicle as a unit.

1. Mount engine in stand and clamp it securely so that the engine can be turned over when necessary. Remove the lifting attachment.
2. On conventional transmission models:
   • Remove bolts attaching transmission to clutch housing. Remove transmission. NOTE: Support the transmission as the last mounting bolt is removed and as it is being pulled away from the engine to prevent damage to clutch disc.
   • Remove flywheel underpan extension and clutch release link from clutch fork.
   • Remove throwout bearing from clutch fork and remove fork.
   • Install Clutch Pilot J-5824 to support clutch during disassembly. Loosen clutch to flywheel bolts a turn at a time (to prevent distortion of clutch cover) until the diaphragm spring pressure is released. Remove all bolts, pilot tool, cover assembly and disc.
   • Remove starter assembly and engine ground strap.
   • Remove the flywheel and clutch housing.
3. On all models equipped with a Powerglide transmission, proceed as follows:
   • Remove two upper transmission to converter housing bolts, install lift sling J-4262 and attach chain hoist to lift sling.
   • Remove spark plugs and wires, and remove flywheel cover and flywheel underpan extension.
   • Remove three flywheel to converter bolts, working through bolt access hole on left side of flywheel housing adjacent to cylinder block drain cock. NOTE: Do not remove converter cover bolts which extend through holes in flywheel.
   • Remove converter housing to flywheel housing bolts and separate transmission assembly from engine. Install Converter Assembly Holding Tool J-5384.
4. Remove octane selector retaining screw and disconnect vacuum line from vacuum spark control. Disconnect spark plug wires from spark plugs and lift the distributor up out of engine.
5. Disconnect gas line from fuel pump, remove fuel pump bolts and fuel pump.
6. Disconnect fuel and vacuum lines from clip at water outlet and from carburetor and remove lines.
7. Remove spark plugs, push rod cover, and oil gauge rod. Remove two bolts attaching water outlet to thermostat housing and remove water outlet and thermostat.
8. Remove two bolts attaching thermostat housing and remove water outlet and thermostat.
9. Remove two bolts attaching thermostat housing to cylinder head and remove housing.
10. Remove water pump retaining bolts and remove generator brace and pump.
11. Attach Harmonic Balancer Puller J-1287-A to balancer and turn puller screw to remove balancer and pulley assembly.
12. Disconnect throttle rod from throttle and accelerator lever and remove throttle rod.
13. Remove throttle and accelerator lever, and accelerator rod from cylinder block.
14. Remove carburetor attaching nuts and carburetor.
15. Remove nuts and cap screws attaching manifold to cylinder head and remove manifold assembly and gaskets.
16. Disconnect rocker arm shaft oil line at cylinder block and remove oil line.
17. Remove valve lifters.
18. Remove rocker shaft assembly and push rods.
19. Remove the cylinder head attaching bolts, cylinder head and gasket,
20. Using Valve Lifter KMO-642, compress the valve springs and remove valve keys, spring caps, oil seals, springs and valves (fig. 9).
21. Remove the timing gear cover attaching screws and the two bolts that are installed from the back through the front main bearing cap and remove cover and gasket.
22. Pull the crankshaft gear with Gear Puller T-126-R by attaching it to the gear and turning the puller handle (fig. 26).
23. Remove the two camshaft thrust plate screws by working through holes in the camshaft gear (fig. 27).
24. Remove the camshaft and gear assembly by pulling it out through the front of the block. NOTE: Support shaft carefully when removing so as not to damage camshaft bearings.
25. Remove the engine front mounting plate attaching screws and remove plate and gasket.
26. Disconnect oil pump to block oil line from pump and block fitting and remove oil line.
27. Remove oil pump retaining screw and remove oil pump.
28. Remove oil pump cover attaching screws, cover, gasket, idler gear and drive gear and shaft.
29. Check the connecting rods and pistons for cylinder number identification and, if necessary, mark them.
30. Remove connecting nuts and rod caps. Push the rods away from the crankshaft and install caps and nuts loosely to their respective rods.
31. Push piston and rod assemblies away from crankshaft and out of the cylinders. Remove ridge at top of cylinder bore if necessary. NOTE: It will be necessary to turn the crankshaft slightly to disconnect some of the rods and to push them out of the cylinder.
32. Remove piston rings by expanding them and sliding them off the ends of the pistons.
33. Clamp the piston in Piston Vise J-1218 (fig. 28), remove the connecting rod to piston pin clamp bolt and push the piston pin out (all pistons).
34. Remove main bearing cap bolts and remove the bearing caps and shims.
35. Lift the crankshaft out of the block and place it where it will not get damaged.
36. Lift bearing shells from block and bearing cap.

1. Wash all parts thoroughly in cleaning solvent.
2. Remove oil gallery plugs, located one at front and one at rear face of cylinder block. These plugs may be removed with a sharp punch or they may be drilled and pried out. This oil passage should be thoroughly cleaned either by using compressed air or wire brush.
3. Clean all oil passages in the cylinder block and crankshaft by blowing them out with compressed air. It is good practice to blow them out separately. On the block this can be done by plugging the holes in three of the bearings and placing the nozzle of the air gun in the oil inlet of the cylinder block and blowing through the remaining bearing oil passages. Continue this until all passages are clean. Blow through the passage to the camshaft bearings.
4. Run a fine wire through the cylinder wall lubrication holes in each connecting rod.
5. Blow out the rocker arm shaft oil line, and the passage up from the rear camshaft bearing.
6. Clean carbon from piston heads, ring grooves and inside of piston head. Clean carbon from cylinder head combustion chambers and valve ports with Carbon Removing Brush KMO-7004. Clean valve guides with Valve Guide Cleaner KMO-122. Clean valve stems and heads on a buffing wheel.
7. Check the cylinder block for cracks in the cylinder walls, water jacket and main bearing webs.
8. Check the cylinder walls for taper, out-of-round or excessive ridge at top of ring travel. This should be done with a dial indicator (fig. 29). Set the gauge so that the thrust pin must be forced in about 1/4" to enter gauge in cylinder bore. Center gauge in cylinder and turn dial to "0." Carefully work gauge up and down cylinder to determine taper and turn it to different points around cylinder wall to determine the out-of-round condition.
9. Set the indicator to the standard cylinder size using a pair of micrometers. Then, by checking the cylinders, the oversize pistons required and the amount necessary to be removed from the cylinders can be determined.
10. Inspect the main bearing shells for wear or damage that would make replacement necessary.
11. Inspect camshaft bearings for wear or damage.
12. Inspect the camshaft for damaged cams or bearing journals. If the journals are out-of-round more than .001" the shaft should be replaced. Check the fit of the camshaft in the bearings.
13. Inspect the crankshaft journals and crank pins for roughness and scores. Check them with a micrometer of out-of-round or taper. If out-of-round more than .001" or tapered, the shaft should be replaced or reconditioned.
14. Inspect the connecting rod bearings for damage that would make replacement necessary.
15. Determine whether or not pistons are to be replaced. New piston assemblies and rings are required when the cylinders are to be honed or rebored. If the pistons are to be used again, check the piston pin fit in the pin bores.
16. Inspect the timing gears for excessive tooth wear and for loose hub in camshaft gear. Inspect the camshaft thrust plate for excessive wear.
17. Check the cylinder head for being warped, for having clogged water passages, cracked valve seats or worn valve guides.
18. Inspect the manifolds for excessive carbon in the ports. Check the operation of the heat control valve and make sure that the gasket between the manifolds is in good condition.
19. Inspect the oil pump gears for wear, check the shaft for looseness in the loosen and the inside of cover for wear that would permit oil to leak past end of gears. Check screen for damage.
20. Instructions for inspection and repair of the fuel pump, carburetor, air cleaner, generator, starting motor, distributor, clutch and water pump will be found in their respective sections of this manual.

General Information

Some of the following repair operations may not be required on all engine overhauls, depending upon the result of the inspections made. In making some of the repairs, certain engine assembling operations must be performed; therefore, the assembling operations will start with the engine partly assembled as covered under repair operations.

If the cylinder block inspection indicated that the block was suitable for continued use except for out-of-round or tapered cylinders, they can be conditioned by honing or boring and honing.

High limit standard size pistons are available for service use so that proper clearances can be obtained for slightly worn cylinder bores and blocks requiring only light honing to clean up the bores. There are four standard size pistons available for service under two part numbers. These aluminum pistons are selected by size and are unitized in groups of six for service usage. In addition, aluminum pistons are serviced in .020", .030" and .040" oversizes. If the cylinders were found to have less than .005" taper or wear they can be conditioned with a hone and fitted with the high limit standard size pistons. A cylinder bore of less than .005" wear or taper may not entirely clean up when fitted to a high limit position. If it is desired to entirely clean up the bore in these cases, it will be necessary to rebore for an oversize piston. If more than .005" taper or wear they should be bored and honed to the smallest oversize that will permit complete resurfacing of all cylinders. The use of a dial gauge set up with a pair of micrometers to the standard cylinder bore size as outlined under "Cleaning and Inspection," will aid in determining the size pistons for which the cylinders must be bored.

Cylinder Boring

1. Before using any type boring bar, the top of the cylinder block should be filed off to remove any dirt or burrs. This is very important. Otherwise, the boring bar may be tilted which would result in the rebored cylinder wall not being at right angles to the crankshaft.
2. In Chevrolet engines, the piston clearance is provided for on the piston and this must be taken into consideration when setting the cutter in the boring bar. The piston to be fitted should be checked with a micrometer, measuring just below the lower ring groove and at right angles to the piston pin. The cylinder should be bored to the same diameter as the piston.
3. If a micrometer is not available to measure the piston, the cylinder should be bored .002" less than the oversize piston to be fitted. For example, when fitting a .020" oversize piston, the cylinder should be bored .018" over standard.
4. The instructions furnished by the manufacturer of the. equipment being used should be carefully followed.

Cylinder Honing and Piston Fitting

1. When the cylinders are to be honed only for use of standard high limit piston or for final finishing after they have been rebored to within .002" of the desired size, they should be finish honed and polished with a hone. Rough stones may be used at first and fine stones for the polishing operation.
2. Place the hone into a cylinder bore and expand the stones until the hone can just be turned by hand. Connect a 3/4" electric drill to the hone and drive hone at drill speed while slowly moving hone up and down entire length of cylinder until hone begins to run free. During this operation a liberal amount of kerosene should be used as a cutting fluid to keep the stones of the hone clean.
3. Expand the stones against the cylinder bore and repeat the honing operation until the desired bore diameter is obtained.
4. Occasionally during the honing operation, the cylinder bore should be thoroughly cleaned and the piston selected for the individual cylinder checked for correct fit.
5. Check fit of the aluminum pistons in the following manner:
   • Invert the piston, skirt end up, and place a .0015" by 1/2" wide feeler ribbon, part of Piston Fitting Gauge and Scale Tool, J-5513 on the side of the piston 9' from the piston pin holes.
   • Insert the feeler ribbon and inverted piston into the cylinder bore so that the center of the piston pin is flush with the top surface of the cylinder block. Keep the feeler ribbon straight up and down and keep the piston pin parallel with the crankshaft axis.
   • Pull the feeler gauge straight up and out, noting at the same time the scale reading which should be between 7 and 18 pounds (fig. 30).
   • If the scale reading is greater than the maximum allowable pull, try another piston or lightly hone the cylinder bore to obtain the proper fit.
   • Should the scale reading be less than the minimum allowable pull, try another piston, or if standard size, try a standard high limit piston. If proper fit cannot be obtained, it will be necessary to rebore the cylinder to the next oversize piston.
   • Mark each piston after fitting to correspond with the cylinder to which it has been fitted. This will assure proper installation.
6. Permanently mark the piston for the cylinder to which it has been fitted and proceed to hone cylinders and fit the remaining pistons. CAUTION: Handle the pistons with care and do not attempt to force them through the cylinder until the cylinder has been bored to correct size as this type piston can be distorted through careless handling.
7. Thoroughly clean the cylinder bores. It is extremely essential that a good cleaning operation be performed. If any of the abrasive material is allowed to remain in the cylinder bores, it will rapidly wear the new rings and cylinder bores in addition to the bearings lubricated by the contaminated oil. The bores should be swabbed several times with light engine oil and a clean cloth and then wiped with a clean dry cloth. Cylinder should not be cleaned with kerosene or gasoline. Clean the remainder of the cylinder block to remove the excess material spread during the honing operation.

Piston Pin Fitting

All new Chevrolet pistons are serviced with properly fitted piston pins, therefore, pin fitting is unnecessary when new pistons are installed. Where cylinder condition and piston fit justify the use of old pistons, it may be desirable to install new piston pins which are available in .0015", .003" and .005" oversize. Correct alignment of the pin bores is essential; therefore, the following procedure should be carefully followed.

1. Adjust the expansion reamer for a light cut and clamp square end in bench vise.
2. Place piston over reamer and start reamer pilot in piston pin bores (fig. 31).
3. Turn the piston until the reamer has passed through both bores.
4. Expand the reamer by easy stages and repeat the reamer operation until the piston pin is fitted.
5. Stabilize the temperature of the piston and piston pin by immersion in oil at 70F.
6. Wipe the piston and pin dry, and lightly coat the pin with an oil film.
7. Place one end of the pin in either boss.
8. The fit must be such that the pin will hold its own weight in either boss and yet permit movement under thumb pressure in its final position (fig. 32).
9. If pin is too tight, lightly hone pin hole.
10. If pin is too loose, ream to next oversize pin. After fitting the first piston pin, the other bores may be reamed quickly by reducing the diameter of the reamer approximately .0005" (half a thousandth) by backing off the expansion screw. This permits quick roughing out of all bores leaving about half a thousandth for the finish cut.
11. It is good practice to check the diameter of all piston pins with a micrometer. In case there should be a slight variation in diameter, consideration must be taken when adjusting the reamer for the finish cut.

The camshafts are of cast alloy iron with the following bearing journal sizes: front 2.1537" - 2.1547"; front intermediate 2.0912"-2.0922"; rear intermediate 2.0287"-2.0297"; rear 1.9662"-1.9672".

These dimensions should be checked with a micrometer for an out-of-round condition. If the journals exceed .001" out-of-round, the camshaft should be replaced.

The camshaft should also be checked for alignment. The best method is by use of "V" blocks and a dial indicator (fig. 33). The dial indicator will indicate the exact amount the camshaft is out of true. If it is out more than .002" dial indicator reading, the camshaft should be straightened. When checking, the high reading of the dial indicator indicates the high point of the shaft. This point should be chalk marked to tell exactly where to apply pressure when straightening.

NOTE: During the straightening operation, care should be taken to protect the bearing journals and prevent damage of their surfaces. Use care to avoid breakage of the cast iron camshaft.

After the camshaft has been straightened, it should be rechecked to be sure it is within .002" dial indicator reading for alignment.

Camshaft Bearings (6 Cylinder Engine)

On six cylinder engines camshaft bearing removal and installation is accomplished in one operation with tool numbered J-6356. This tool has adapters to fit all six cylinder engines from 1937 to 1956. With this tool, the front two bearings are replaced first, then the rear two bearings are replaced. The tool has been engineered for the precision type camshaft bearings used in all 6 Cylinder Chevrolet Engines.

Replacement (6 Cylinder Engine)

1. With camshaft removed, drive out expansion plug from cylinder block at the rear of the rear camshaft bearing, by driving it out from the inside.
2. Install a bearing Replacer in first and second camshaft bearing with new bearing installed on trailing edge of each Replacer. Trailing edge of Replacer should be towards center of engine.
3. Assemble tool with nut and washer on rear of screw shaft.
4. Index assembled tool through camshaft bearing Replacer in number 2 bearing, then turn nut on screwshaft to end of threads. While turning nut on screwshaft, install washer on front of shaft and feed screwshaft through Replacer in number 1 bearing.
5. Install bracket and thrust bearing on front of screwshaft and install remaining nut on screwshaft. Tighten nut until all threads are engaged.
6. Tighten nut behind number 1 bearing Re- placer snugly. Repeat operation for number 2 Replacer.
7. Using two wrenches, hold screwshaft with one wrench while turning the front nut with the other. Pull new bearing into place, washer will act as bearing stop.

   CAUTION: Align oil holes in bearings with oil holes in block before pulling into place.

8. Disassemble tool and repeat operation for rear two camshaft bearings.

The upper half of the rear bearing cap oil seal, located in the cylinder block, can only be replaced with the crankshaft removed from the block. See Oil SeaI-Rear Bearing Cap under Care, Maintenance and Adjustments for replacing oil seal in bearing cap.

1. Remove old wick seal from groove in block and make sure groove is thoroughly cleaned.
2. Install new wick seal in groove with the fingers.
3. Use a rounded tool and roll the seal into the groove starting at one end and roll it to the center. Then starting from the other end again roll to the center.
4. Cut the small portion of the seal that protrudes from the groove off flush with surface of the bearing. NOTE: A round block of wood the same diameter as the crankshaft flange should be used to hold the packing firmly in position in the groove while the ends are being cut off.

The crankshaft main bearing journal and connecting rod journal sizes are as follows: front, 2.6835"-2.6845"; front intermediate, 2.7145"-2.7155"; rear intermediate, 2.7455"-2.7465"; rear, 2.7765"-2.7775"; connecting rod journal, 2.311-2.312".

These dimensions should be checked with a micrometer for out-of-round taper or undersize. If the journals exceed .001" out-of-round or taper the crankshaft should be replaced or reconditioned to an undersize figure that will enable the installation of undersize precision type bearings.

The crankshaft should also be checked for runout. To perform this operation, support the crankshaft at the front and rear main bearing journals in "V" blocks and indicate the runout of both the rear intermediate and front intermediate journals, using a dial indicator. The runout limit of each of these journals is .002". If the runout exceeds .002" the crankshaft must be straightened.

Main Bearings

Precision type main bearings used as service replacement are of high quality with close tolerances of fit and do not require line reaming on installation. The close dimensional tolerances assure an equalized bearing surface at all points on the crankshaft when replaced in sets. Bearings are available in standard sizes and undersizes of .002", .010", .020" and .030".

Precision type main bearings may be replaced either with the engine in the vehicle or with the engine removed. With the engine in the vehicle, proceed as outlined below.

1. Remove harmonic balancer and timing gear cover as previously outlined.
2. Remove rocker arm cover and loosen all rocker arm screws to relieve tension on camshaft.
3. Remove spark plugs.
4. Remove transmission from vehicle (see Section 7 of this manual).
5. Drain the oil, remove the oil pan and oil pump.
6. Rotate crankshaft to best possible position for removal of all bearing caps and mark the meshing teeth of the timing gears so that they can be remeshed in the same position.
7. Loosen all four main bearing cap bolts evenly until the crankshaft is lowered approximately 3/8".
8. Remove front intermediate and rear bearing caps and remove upper and lower bearing shells. If upper bearing shells do not come away with the crankshaft, tap lightly to loosen. NOTE: Always replace bearings in pairs. In this way two bearings are supporting the crankshaft while you are working on the other two.
9. Install new upper half bearing shells in rear and front intermediate bearing bores by rolling into position, centering, and pressing up into place. If the bearings have the correct spread, they will snap into place and stay there. NOTE: Be sure to install all upper bearing halves so the smaller of the two oil holes will be toward the camshaft when the bearing halves are rolled into place.
10. Install new lower half bearing shells in rear and front intermediate bearing caps and replace caps, using three .002" shims on each side of bearing as a starting point for adjustment. Lubricate bearings with light engine oil. Draw bolts up until caps are snug to crankshaft bearing journals.
11. Remove front and rear intermediate bearing caps and remove upper and lower bearing shells. If upper bearing shells do not come away with the crankshaft, tap lightly to loosen.
12. Install new upper half bearing shells in front and rear intermediate bearing bores by rolling into position, centering, and pressing up into place. NOTE: Due to close side fit, the upper half of the rear intermediate bearing may not go all the way into place. Start it evenly and it will go all the way into place when the crankshaft is raised.
13. Install new lower half bearing shells in front and rear intermediate bearing caps and replace caps using three .002" shims on each side of bearing. Draw bolts up until caps are snug to crankshaft bearing journals.
14. After all main bearings have been replaced, raise the crankshaft by tightening the bearing cap bolts alternately and evenly. NOTE: At the some time, check the meshing of the timing gears, turning the camshaft gear as necessary so that the gears engage with the previously installed marks (step 6) aligned.
15. With the crankshaft up in place, force it all the way fore or aft and check the end clearance at the rear intermediate bearing (fig. 34).This should be .003" to .009".
16. Adjust main bearings as outlined under Minor Service Operations, Main Bearings Adjust.
17. Replace oil pump and lines.
18. Install transmission (see Section 7 in this manual).
19. Adjust and replace spark plugs.
20. Replace harmonic balancer and timing gear cover as previously outlined.
21. Tighten rocker arm screws, start the engine and after it has normalized, adjust the valve clearances. Install the valve cover.

-Adjust

Plastigage consists of a wax-like plastic material which will compress evenly between the bearing and journal surfaces without damaging either surface. To obtain the most accurate results with Plastigage, certain precautions should be observed. If the engine is out of the chassis and upside down, the crankshaft will rest on the upper bearings and it can be assumed that the total clearance can be measured between the cap bearing and journal.

NOTE: To assure the proper seating of the crankshaft, remove rear main bearing oil seal. In addition, preparatory to checking fit of bearings the surface of the crankshaft journal and bearing should be wiped clean of oil. If the Plastigage check is to be made on engine in the chassis, the crankshaft must be supported by a jack or blocks, up against the upper bearings.

1. Starting with the rear main bearing, remove bearing cap and wipe oil from journal and bearing cap. NOTE: The other bearings must be left at their specified torque.
2. Place a piece of Plastigage the full width of the bearing (parallel to the crankshaft) on the journal (fig. 35).
3. Install the bearing cap and shims removed and evenly tighten the retaining bolts to 100-110 ft. lbs. torque. CAUTION: Do not rotate the crankshaft while the Plastigage is between the bearing and journal.
4. Remove bearing cap, the flattened Plastigage will be found adhering to either the bearing shell or journal. On the edge of Plastigage packing envelope there is a graduated scale which is correlated in thousandths of an inch.
5. Without removing the Plastigage, check its compressed width (at the widest point) with the graduations on the Plastigage envelope (fig. 36). NOTE: Normally, main bearing journals wear evenly and are not out-of-round. However, if a bearing is being fitted to an out-of-round journal be sure to fit to the maximum diameter of the journal. If the bearing is fitted to the minimum diameter of the journal and the journal is out-of-round .001' or more, interference between the bearing and journal will result in rapid bearing failure. If the flattened Plastigage tapers toward the middle ends, there is a difference in clearance indicating a taper, low spot or other irregularity of the bearing or journal. Be sure to check the journal with a micrometer if the flattened Plastigage indicates more than .001" difference.
6. If the bearing clearance is not over .004" old, .003" new or less than .001" the bearing insert is satisfactory. If the clearance is not within these limits, selective fit bearing by removing or inserting. NOTE: When adjusting main bearings if is a good practice to remove the shims evenly. However, should it be necessary to use an uneven number of shims, the greater number of shims should be on the same side of all bearings.
7. If removal of shims does not bring the clearance below .004" it will be necessary to regrind the crankshaft journal for use with the next undersize bearing. NOTE: Bearings are available in standard sizes and .002", .010", and .020' and .030" undersize.
8. New bearing shell clearance should be .003" maximum and .001" minimum.
9. After adjusting rear main to specifications, proceed to next bearing. After all bearings have been adjusted, check to see that there is no excessive drag on the crankshaft. NOTE: When installing front main bearing cap, timing gear cover through-bolts should be tightened before bearing cap bolts to assure seal between cap and front end plate.
10. Install new rear bearing oil seal.
11. Install front end plate and gasket and crankshaft gear.

Timing Gear Oil Nozzle

Examine the tin-timing gear oil nozzle, which is of tubular construction, and pressed and flared in place in the cylinder block front end plate.

In the event the oil nozzle is damaged it will be necessary to replace the front end plate assembly as it is not practical to replace the nozzle only without the use of special equipment.

Cylinder Block Front End Plate

1. Install new oil gallery plugs at front and rear face of block making sure they seat properly.
2. Install new front end plate gasket and end plate, and hold in position with three screws and two hex head bolts. Tighten screws to 15-20 ft. lbs. and stake securely at bottom of slot.

NOTE: Make sure gasket surfaces on block and on end plate are thoroughly cleaned.

Crankshaft Gear-Install

1. Place the two woodruff keys in their respective keyways in the crankshaft.
2. Place the crankshaft gear on the end of crankshaft with keyway in line with key.
3. Drive the gear onto the shaft, using a suitable driver until gear bottoms against shoulder on shaft.

Camshaft Gear and Thrust Plate

1. If the inspection indicated that the camshaft, gear and thrust plate were in good condition, the camshaft end play should be checked (fig. 37). This clearance should be .001" to .005"".
2. If the inspection indicated that the shaft, gear or plate should be replaced, the gear must be removed from the shaft. This operation requires the use of Camshaft Gear Remover J-971-A.
3. Place the camshaft through the gear remover, place end of remover on table of a press and press shaft out of gear (fig. 38). CAUTION: Thrust plate must be so positioned that woodruff key in shaft does not damage it when the shaft is pressed out of gear. Also, support on the hub of the gear or the gear will be seriously damaged.
4. To assemble camshaft gear, thrust plate and gear spacer ring to camshaft, proceed as follows:
   • Firmly support shaft at back of the front journal in an arbor press.
   • Place gear spacer ring and thrust plate over end of shaft, and install woodruff key in shaft keyway.
   • Install camshaft gear and press it onto the shaft until it bottoms against the gear spacer ring. The end clearance of the thrust plate should be .001" to .005".
5. Install the camshaft assembly in the engine block, being careful not to damage bearings or cams.
6. Turn crankshaft and camshaft so that the valve timing marks on the gear teeth will line up and push camshaft into position. Install camshaft thrust plate to block screws and tighten them securely.
7. Check camshaft and crankshaft gear runout with a dial indicator (fig. 39). The camshaft gear runout should not exceed .004" and the crankshaft gear runout should not exceed .003".
8. If gear runout is excessive, the gear will have to be removed and any burrs cleaned from the shaft or the gear replaced.
9. Check the backlash between the timing gear teeth with a narrow feeler gauge (fig. 40). The backlash should not be less than .004" nor more than .006".

Cover

1. A spring loaded oil seal is pressed into the crankshaft opening of the timing gear cover to prevent oil leakage around the hub of the harmonic balancer.
2. If this seal shows signs of wear or damage, it should be replaced by prying it out of the cover from the front with a large screwdriver.
3. Install new seal so that open end of the seal is toward the inside of the cover and drive in place with Oil Seal Driver J-995 (fig. 21).
4. Make certain that cover mounting face and cylinder block front end plate face are clean.
5. Install Timing Gear Cover Centering Gauge J-966 over end of crankshaft.
6. Coat the oil seal with light grease and using a new cover gasket install cover and gasket over centering gauge.
7. Install cover screws and two bolts through bearing cap and tighten to 6-7 1/2 foot pounds torque using a torque wrench. Remove centering gauge. NOTE: It Is important that the centering gauge used to align the timing gear cover so that the harmonic balancer installation will not damage the seal and to provide uniform seal tension on the hub of the balancer.

Installation

1. Remove puller screw from harmonic balancer.
2. Install two 3/8"-16 x 1" bolts in harmonic balancer.
3. Line up keyway in balancer with key on crankshaft and drive balancer onto shaft until it bottoms against crankshaft gear using J-5590, Transmission Front Bearing Installer (fig. 41).
4. Remove two 3/8"-16 bolts.

Installation

Models with Standard Transmissions or Overdrive

1. Install clutch housing and attaching bolts and tighten to 45-55 foot pounds with a torque wrench.
2. Install indicator extension in a crankshaft stud hole, attach indicator to extension and check pilot hole runout (fig. 42). This runout should not exceed .008".
3. Should runout exceed .008" the clutch housing should be aligned as outlined for flywheel housing, Powerglide models.
4. Remove indicator and indicator extension.

Flywheel Housing-Powerglide Models

The flywheel housing used on Powerglide models differs from the regular production clutch housing in both design and tolerances. Parallelism of the face must be within .007" and total bore runout must not exceed .005". Special oversize dowel pins are to be used to obtain proper bore runout with respect to the crankshaft bearings.

Procedure for installing this flywheel housing and checking alignment correction is as follows. In addition, this method of alignment correction may be applied to correct bore n-misalignment, where found, of the clutch housing on standard or overdrive transmission models.

1. Remove old flywheel housing from cylinder block.
2. Carefully clean mating surfaces of block and new housing of dirt, burrs, nicks, etc.
3. Install new flywheel housing to block, install attaching bolts and tighten evenly to 45-55 ft. lbs. torque,
4. Install indicator post J-2494 in one of the crankshaft flange stud holes. Attach swivel J-4656-1, swivel sleeve J-4656-3 to indicator post. NOTE: Swivel, swivel sleeve and indicator extension rod are part of swivel set J-4656 designed for this alignment check.
5. Install indicator KMO 30-B to indicator extension rod and set indicator to read zero at the six o'clock position on the flywheel housing face (fig. 43).
6. Indicate face of housing and take readings at the 9, 12 and 3 o'clock positions. The runout limit is .007". NOTE: Care should be exercised so that the indicator button is not on the edge of a bolt hole when the readings are taken.
7. Reset the indicator to read zero at the six o'clock position on the machined inside diameter of the flywheel housing bore, being careful that the indicator button is centered on the narrow machined flange and does not touch flange step.
8. Take readings at the 9, 12, and 3 o'clock positions, carefully lifting indicator button over each cutaway section of flange. The runout should not exceed .005" (fig. 44).

Alignment Correction

NOTE: When applying this alignment correction to clutch housing of a standard or overdrive transmission engine, face parallelism should be disregarded as this alignment check must be made with the transmission case assembled to housing in the normal manner. This alignment correction is covered in the transmission section.

1. If bore runout is in excess of .005" or if housing face parallelism exceeds .007", remove indicator and the flywheel housing from the engine block.
2. Remove the lower left hand dowel by driving it out, using a drift punch through hole in cylinder block flange.
3. Center punch the other two dowels and then drill through the dowels using a 7/32" drill.
4. Run a 1/4"-28 tap through drilled holes in dowels.
5. Install a 1/4"-28x2 capscrew into each dowel. Tighten capscrew to push dowels out of block.
6. Clean mating faces of flywheel housing and engine block and make certain there are no burrs or metal extrusion around dowel or bolt holes.
7. Install flywheel housing and tighten attaching bolts evenly to 45-55 ft. lbs. torque.
8. Mount indicator on indicator post and indicate flywheel housing face. Set indicator at zero at the six o'clock position and carefully check indicator readings at the 9, 12, and 3 o'clock positions. The runout limit is .007". NOTE: Care should be exercised so that the indicator button is not on the edge of a bolt hole when the readings are taken.
9. If the face runout exceeds .007", shim as necessary, using main bearing shim No. 3847687 between the housing and block at the attaching bolt locations.
10. After the housing face has been brought within the .007" limit, with bolts tightened to required torque, reset indicator to read zero at the six o'clock position on the machined inside diameter of the flywheel housing bore. NOTE: Be careful that the indicator button is centered on the narrow machined flange and does not touch flange step.
11. Check indicator readings at the 9, 12, and 3 o'clock positions, carefully lifting indicator button over each cutaway section of flange. The runout should not exceed .005".
12. If the readings exceed the .005" runout limits, loosen bolts slightly and tap housing with a soft hammer in required direction until runout is within limits. Tighten attaching bolts evenly to 45-55 ft. lbs. torque and recheck.
13. With flywheel housing in proper alignment, carefully drill through dowel holes in housing and into block using a 1 3/32" drill. CAUTION: When drilling into lower right blind hole in block, be careful not to drill through.
14. Carefully ream holes using J-4628 reamer (27/64").
15. Blow out holes and then install 27/64" oversize dowels.
16. Recheck flywheel housing bore and the face to make sure they are still within proper limits.

Flywheel Installation

1. Clean the mating flanges of flywheel and crankshaft carefully and make sure there are no burrs on either mounting face.
2. Place the flywheel in the clutch housing and position it so that the three evenly spaced dowels in crankshaft flange will enter the holes in the flywheel.
3. Install the six bolts using new lock plates under each pair of bolts.
4. Tighten bolts to 50-65 foot pounds with a torque wrench.
5. On all except Powerglide models, mount a dial indicator on the clutch housing so that the button of the indicator will contact the machined surface of flywheel (fig. 45), and check the flywheel runout.
6. Runout should not exceed .008". If excessive, remove flywheel and recheck for burrs or replace flywheel.
7. Securely lock the mounting bolts by bending the lock plates up against the bolt heads.

Connecting Rod Alignment

Correct alignment of the connecting rods is important. Whether new rods are being used or the old ones reinstalled, they must be checked for alignment.

1. Place the piston pin in the eye of the connecting rod and tighten the clamp bolt.
2. Place the connecting rod on the arbor of the aligning fixture J-3210-A, and tighten the connecting rod bolts.
3. Place the "V" block on the piston pin and move the rod and arbor toward the face plate until the pins on the "V" block just engage the face plate (fig. 46). If all pins touch the face plate the rod is in alignment.
4. If either the top or the bottom two pins touch the face Plate, but the other two do not, the rod is bent.
5. If only the two pins on the front or the two on the back side of the "V" block touch the face plate, the rod is twisted.
6. The fixture is sufficiently strong to hold the connecting rod for straightening. Place a bending bar (HM 3-R) on the rod and twist or bend the rod as required and recheck. Continue this operation until all pins just touch the face plate.
7. Place the "V" block on the piston pin so that the "V" block rests against the outside edge of the connecting rod and move the rod and "V" block toward the face plate until all four pins touch.
8. Place the index on the bottom of the fixture so that it touches the large end of the connecting rod bearing. Remove the rod from the arbor and turn it around.
9. Assemble it again to the arbor and place the "V" block on the piston pin in the same place as when checking the other side. Move rod and "V" block toward the face plate until either the index touches the bearing or the pins touch the face plate.
10. If the index does not touch the rod bearing with the four pins touching the face plate, check the distance between the rod bearing and the index with a feeler gauge. If this distance is greater than .025" the rod should be straightened until pins touch the face plate and the index touches the rod bearing within .025".
11. If the index touches the rod bearing and the four pins do not touch the face plate, the distance between the pins and the face plate should also be checked with a feeler gauge. If this distance is more than .025" the rod should be straightened until the pins on the "V" block touch the plate and the index touches the rod bearing within .025".

Assemble Connecting Rod to Piston

1. Place the piston in piston vise J-1218. Assemble the rod to the piston and install the piston pin. Before tightening the clamp screw, center the piston pin in the piston and the connecting rod in the center of the two piston pin bosses.
2. Tighten the clamp screw and move piston on pin from side to side, checking to see that the piston pin does not extend beyond the outside of the piston.
3. Assemble remaining rods to pistons. NOTE: The connecting rod should never be clamped in a bench vise when installing the piston on it as tightening the clamp screw will likely twist the rod.

Check Rod and Piston Alignment

1. Assemble the piston and connecting rod assembly to the alignment fixture (fig. 47) and check with the "V" block resting against the piston skirt to see that the rod and piston are in alignment. Both pins on the "V" block should rest against the face of the plate on the fixture. The piston should be in the same alignment as the connecting rod when this check is made.
2. A quick check of a piston and connecting rod assembly for both cock and twist can be made without disassembling the rod from the piston. This method saves considerable time on any repair operation that does not normally require the removal of the rod from the piston.
3. To make this check, the connecting rod and piston assembly is mounted on the alignment fixture and the piston is set in line with the connecting rod. Then place the "V" block on the piston skirt. If both pins on the block contact the face plate, the rod is not cocked (fig. 47).
4. Then, with the "V" block on the piston skirt and the pins against the face plate, tip the piston first in one direction and then in the other (fig. 48). If the pins on the block remain against the face plate, there is no twist in the connecting rod.
5. If one pin leaves the face plate while the piston is being tipped in one direction and the other pin leaves the face plate while the piston is being tipped in the other direction, the connecting rod is twisted and should be straightened until both pins follow the face plate.

Piston Ring Fitting

Flex type oil control rings are now used in all Chevrolet engines. Previously the oil control ring was a four piece ring with an expander placed behind the separator. The new flex type oil control ring consists of two rails and a flexible segmented spacer that serves as a combination spacer and expander on the rails. Constant pressure is maintained on cylinder walls by the rails which are held firm but not rigidly by the flexible spacer; severe ring pressure is averted to increase ring and cylinder wall wear.

This type compression ring takes its name, twist type, from its installed position which is cocked or twisted. It assumes and maintains this position for life because the upper edge of its diameter is chamfered, making the ring unbalanced in cross section

All compression rings are marked with the word "TOP" cast in the upper side of the ring. When installing compression rings, make sure the side marked "TOP" is toward the top of the piston.

The oil control rings are of four piece construction. These parts are an upper rail, a lower rail, a crimped spring steel spacer between the two rails and an expander behind the spacer and rails. Production rings have an octagonal spring steel expander while service rings have a crimped steel expander.

Chevrolet piston rings are furnished in standard sizes as well as .020", .030" and .040" oversizes.

Compression Ring Installation

1. Select rings comparable in size to the pistons being used.
2. Slip the ring in the cylinder bore; then, using the head of a piston, press the ring down into the cylinder bore about two inches. NOTE: Using a piston in this way will place the ring square with the cylinder walls.
3. Check the space or gap between the ends of the ring with a feeler gauge. This gap should be from .007" to .020".
4. If the gap between the ends of the ring is less than .007", remove the ring and try another for fit, or the gap in the tight fitting ring may be enlarged as follows.
5. Remove the ring from the cylinder, then clamp a fine cut file in a vise and grasping each end of the ring firmly between the thumb and fingers, work the two ends of the ring across the surfaces of the file. Press the ring together at the gap lightly until the proper gap is obtained. Be careful not to distort the ring during this operation or it may bind in the ring groove of the piston. Fit each ring separately to the cylinder in which it is going to be used.
6. New pistons, rings and cylinder bores wear considerably during seating and gaps widen quickly; however, engine operation will not become seriously affected if ring gaps do not become greater than 1/32"
7. Carefully remove all particles of carbon from the ring grooves in the piston and inspect the grooves carefully for burrs or nicks that might cause the rings to hang up.
8. Slip the outer surface of the ring into the piston ring groove and roll the ring entirely around the groove to make sure that the ring is free and does not bind in the groove at any point (fig. 49). If binding occurs, the cause should be determined and removed by carefully dressing with a fine cut file. However, if the binding is caused by a distorted ring, install a new ring.
9. Proper clearance of the piston ring in its piston ring groove is very important in maintaining engine performance and in preventing excessive oil consumption. Therefore, when fitting new rings, the following clearances between the top and bottom surfaces of the ring grooves should be provided.
10. The compression rings should be fitted so that the clearance is .0020" to .0035" (fig. 50).
11. Assemble the rings to the pistons as they are fitted and make a final test of the ring fit in the grooves by repeating the fitting procedure given above.

Expander ends must not align with the ring gap.

NOTE: It is important that each ring be fitted its individual cylinder for proper gap spacing and to its individual piston and groove for proper groove clearance.

Oil Control Ring Installation

1. Install the oil ring spacer in the oil ring groove and position gap in line with piston pin hole. Hold spacer ends butted and install steel rail on top side of spacer. Position gap at least I!' to left of spacer gap, then install second rail on lower side of spacer. Position gap at least I" to right of spacer gap.
2. Flex the oil ring assembly in its groove to make sure ring is free and does not bind in the groove at any point. If binding occurs, the cause should be determined and removed by carefully dressing with a fine cut file. However, if the binding is caused by a distorted ring, install a new ring.
3. Proper clearance of the piston ring in its piston ring groove is very important in maintaining engine performance and in preventing excessive oil consumption. Therefore, when fitting new rings, check the clearances between the top and bottom surfaces of the ring grooves. Refer to "Engine Specifications" for correct clearances.

NOTE: It is important that each ring be fitted to its individual piston and groove for proper groove clearance.

Assemble Pistons and Connecting Rods to Engine

When the rods are being reassembled, they should be installed in the same cylinder from which they were removed and with the stamped number on the camshaft side.

The condition of the crank pins on the crankshaft should be checked when installing new rods. Damaged crankpins can only be corrected by the installation of a new crankshaft, as it is impossible to insure connecting rod bearing life on a damaged crank pin.

1. Lubricate pistons and cylinder bores, remove bearing caps and install piston and rod assemblies using piston inserter KMO-357 (fig. 51). NOTE: Piston and rods must be installed with the piston pin clamp on the camshaft side.
2. Lubricate crank pin and pull connecting rod down onto it, making sure the numbered side of the rod is toward the camshaft.
3. All engines are equipped with precision interchangeable insert bearings and do not require shims. Install the bearing cap with the numbered side toward the camshaft. Assemble and tighten the bearing cap nuts to 35-45 foot pounds of torque.
4. Install remaining piston and connecting rod assemblies as described above.
5. Adjust connecting rod bearings.

Connecting Rod Bearing Adjustment

Connecting rod bearing inserts are available in standard sizes and undersides of .001" to .002", .010" and .020". These bearings are not shimmed and when clearances become excessive the next underside bearing insert should be used. DO NOT FILE ROD OR ROD CAPS.

1. Remove the connecting rod bearing cap.
2. Wipe bearing insert shell and crankpin clean of oil.
3. Place a piece of Plastigage the full width of the bearing or crankpin (parallel to the crankshaft) ( fig. 52).
4. Reinstall the bearing cap and evenly tighten the retaining nuts to 35-45 ft. lbs. torque. CAUTION: Do not turn crankshaft with the Plastigage installed.
5. Remove the bearing cap and without removing the Plastigage, check its width at the widest point with the Plastigage scale (fig. 53). NOTE: If the crankpin is out-of-round be sure to fit the bearing to the maximum diameter of the crankpin. If the flattened plastic is not uniform from end to end in its width, the crankpin or bearing is tapered, has a low spot or some other irregularity. Check the crankpin with a micrometer for taper if the flattened Plastigage indicates more than a .001" difference.
6. If the reading is not over .004" or not less than .001" the fit is satisfactory. If however, the clearances are not within these limits, replace the bearing with the proper underside bearing. NOTE: The insert bearing shells are not adjustable and no attempt should be made to adjust by filing the bearing caps.
7. New bearing shell insert clearance should be .003" maximum and .001" minimum.
8. Rotate the crankshaft after bearing adjustment to be sure the bearings are not too tight.
9. Check connecting rod clearance between upper half of connecting rod and side of crankpin (fig. 54). See engine specifications for clearance.

Oil Pump Assembly

If the inspection indicated excessive oil pump wear it is advisable to replace the entire oil pump. If the old pump is to be used it should be assembled as follows:

1. Place the drive gear and shaft in the pump body and install the idler gear so that the smooth side of gear will be toward the cover.
2. Install a new GENUINE Chevrolet gasket to assure correct end clearance of the gears.
3. Install the cover and attaching screws.
4. Tighten screws securely and check to see that shaft turns freely.

Cylinder Head

Cylinder Head Conditioning

Condition the cylinder head and vales according to procedure given in Care, Maintenance and Adjustments, Cylinder Head and Valve Conditioning.

Rocker Shaft Oil Line Pipe

The rocker shaft oil line pipe extends forward in the push rod compartment from a fitting in the tappet ledge just above the rear camshaft bearing to a fitting at the center of the push rod compartment. To replace this pipe, cut a new pipe to proper length, install new nipples at each end, and install pipe to cylinder block fittings. Then bend pipe to proper contour so that clearance is provided for the push rods and push rod cover.

Engine Assembly

1. Place the oil pump in position in the block fitting. Install the oil pump retaining screw and tighten securely, being sure that the tapered end of screw draws down into the hole in pump body. Tighten lock nut securely.
2. Install the oil pump to block oil line and tighten the connector nuts securely. Fig. 55 shows the installation.
3. Check to see that the crankcase ventilator baffle (attached to block at crankcase breather hole) is not damaged and is securely bolted in place. Turn the crankshaft to see that the camshaft lobes clear the baffle.
4. Check to see that all connecting rod bolt nuts and main bearing bolts are properly tightened. Check to see that the crankcase is clean.
5. Install new oil pan gaskets and end corks. Carefully place the oil pan in position and tighten pan bolts securely. NOTE: Tighten oil pan corner bolts to 12 1/2-15 ft. lbs. Tighten oil pan flange bolts to 6-71/2 ft. lbs.
6. On conventional transmission models:
   • (a) Lubricate the clutch pilot bearing with a small amount of high melting point grease. Place the clutch disc and clutch cover assembly in position and install the Pilot Tool J-5824.
   • (b) Turn the clutch cover until the "X" on the cover lines up with the "X" on the flywheel. Install the attaching bolts loosely and then tighten them a turn at a time to take up the spring pressure evenly and prevent clutch distortion (fig. 56). Tighten bolts to 25-30 ft. lbs. torque and then remove pilot tool
   • (c) Pack the clutch fork ball seat with a small amount of high melting point grease and snap the fork onto the ball with the end extending through opening in clutch housing.
7. Turn engine assembly over in engine stand.
8. Place a new cylinder head gasket on the block following the installation instructions stamped on gasket. This assures alignment of water passages and bolt holes in head and block with openings in gasket. Install two guide pins to position gasket and pilot cylinder head.
9. Carefully place cylinder head in position over guide pins and lower the head into position. Remove guide pins and install all cylinder head bolts and tighten them finger tight.
10. Tighten the cylinder head bolts a little at a time in the order shown (fig. 7). The final tightening should be 90-95 ft. lbs. torque.
11. Install the twelve valve lifters in right side of block.
12. Install push rod cover using a new gasket and tighten attaching screws evenly to 6-7 1/2" ft. lbs. torque.
13. Install new manifold to cylinder head gaskets, intake manifold sleeves, manifold assembly and attaching parts. Tighten clamp bolts to 15-20 ft. lbs. torque and the two end clamp bolts to 25-30 ft. lbs. Check manifold heat control valve as instructed under Care, Maintenance and Adjustments, Engine Tune-Up.
14. Install push rods and rocker shaft assembly.
15. Install water pump using a new gasket and tighten attaching bolts to 25-30 ft. lbs. Install thermostat housing, place thermostat in housing, install new water outlet gasket and water outlet, and install attaching bolts. Tighten bolts securely.
16. Install carburetor and tighten nuts evenly. Place throttle rod in position and connect it to the bell crank and throttle shaft arm.
17. Install crankcase ventilator tube. Connect tube brace to side of crankcase. Install oil gauge rod.
18. Adjust spark plug gaps to .035". Using new gaskets install spark plugs and tighten to 20-25 ft. lbs. torque.
19. Install the fuel pump using a new gasket and tighten attaching bolts to 15-20 ft. lbs. Place the fuel pump to carburetor gas line and the vacuum spark control line in position and connect them to carburetor and clip at water outlet. Connect the gas line to the fuel pump.
20. Install ignition distributor following instructions in Engine-Electrical Section of this manual and connect vacuum line to distributor spark control.
21. On conventional transmission models:
    • Lubricate the recess on the inside of clutch throwout bearing collar and coat the throwout fork grooves with a small amount of graphite grease and place bearing assembly in position on the throwout fork.
    • Carefully clean the mating faces on clutch housing and transmission case. Pilot the clutch shaft of transmission through throwout bearing and into clutch disc and pilot bearing. Work the transmission up against the clutch housing until bearing retainer pilots into pilot hole in clutch housing. Install and tighten the transmission mounting bolts securely. NOTE: Properly support the transmission as it is being installed or the clutch disc may be damaged.
    • Install the clutch housing underpan and retaining bolts.
22. On all models having the Powerglide Transmission, assemble transmission to engine as follows:
    • Lubricate the flywheel pilot with LubriPlate.
    • Raise transmission until converter housing is in approximate position. CAUTION: Extreme care must be taken when bringing transmission into position that flywheel pilot is not bumped in any way.
    • Turn the torque converter until the "X" mark on the turbine cover is lined up with the "X" mark on the flywheel to the nearest attaching bolt hole. NOTE: These marks must be aligned to maintain balance and the marks will not be visible after the assembly has been completed.
    • Align one of the bolt holes in flywheel with the flywheel housing opening. Then remove Converter Assembly Tool J-5384 and with one 5/16" x 24 guide pin installed in converter cover, carefully enter guide pin in flywheel hole that is aligned with housing opening. At the same time, raise or lower transmission to align flywheel pilot. NOTE: Do not attempt to force transmission, when flywheel pilot is properly aligned it will enter "heel easily and housings will come together.
    • Install converter housing to flywheel housing bolts, remove lift sling J-4262 and replace two transmission housing to converter housing bolts.
    • Remove guide pin and install three flywheel to turbine bolts, rotating flywheel as necessary (fig. 57).
    • Install flywheel cover.
23. Using lift kit J-4536-A, install the proper lifting tool. Attach lifting hooks to suitable hoist, release engine from stand and lift engine with hoist.
24. Install starting motor and body ground strap and tighten attaching bolts securely.
25. Install generator loosely and attach slotted brace. Place fan belt over fan and around pump, generator and crankshaft pulleys. Shift the generator to properly align pulleys and tighten anchor bolts. Force the generator away from engine to tighten belt until it has 5/16" free travel midway between generator and pump pulleys. Tighten generator to brace bolt securely to secure generator in position.

1. Lower engine and transmission assembly into chassis as a unit, guiding engine to align supports with frame.
2. Install rear mounts and bolts and snug up bolts.
3. Install front mounts, and tighten nuts against shoulders.
4. Remove lifting attachment, install cylinder head bolts and tighten to 90-95 ft. lbs. Tighten rear mount bolts.
5. Install rocker arm cover gasket, cover and screws with reinforcements.
6. Slide propeller shaft front universal joint on transmission output shaft, raise rear of propeller shaft, index rear universal joint yoke with pinion shaft companion flange and install U-bolts and nuts. Tighten securely.
7. On conventional transmission models: Connect clutch pedal adjusting link to clutch fork and adjust to give 3/4" to 1" free pedal travel.
8. Connect carburetor linkage.
9. On all models having a 3-speed transmission:
   • Connect speedometer cable to speedometer driven gear.
   • Connect transmission control rods to shifter levers on transmission side cover. Adjust control rods as outlined in "Transmission Section."
   • Check transmission lubricant level.
10. On all models having a Powerglide transmission:
    • Connect speedometer cable to speedometer driven gear.
    • Connect transmission control rod to transmission control rod bell crank and adjust rod as outlined in Transmission Section.
    • Install transmission filler tube and dip stick.
    • Check transmission fluid level.
11. Replace exhaust pipe to manifold and tighten attaching bolts securely.
12. Connect wire to oil pressure gauge and install temperature element in cylinder head.
13. Install air cleaner. NOTE: If oil both cleaner is used, disassemble, clean and refill before installing.
14. Attach generator and field wires to generator.
15. Attach gasoline line to fuel pump.
16. Mount coil in position with two coil mounting bolts, tighten bolts to 5-8 ft. lbs. torque.
17. Attach coil wires to distributor.
18. Install battery box and battery. Attach battery cable and ammeter wire to large terminal on solenoid and starter switch wire to small terminal and connect coil wire to coil.
19. Install radiator core support, radiator assembly and wiring harness. Install horns.
20. Install oil cooler lines on all Powerglide models, and connect radiator hoses.
21. Refill radiator and crankcase.
22. Install wiper motor and connect vacuum lines.
23. On all models with standard transmission, start engine and allow to run until properly normalized and adjust valves as outlined under "Valve Adjustment."
24. On all models with the Powerglide transmission, use oil filler tube and funnel J-4264 and fill transmission as follows:
    • Fill transmission with five quarts of Automatic Transmission Fluid, "Type A".
    • Start engine and let idle with transmission selector lever in "N" position. Check oil level and if necessary add oil to bring fluid level to "Full" mark on the dip stick. Do not overfill.
25. On Powerglide equipped cars, place selector lever in reverse and check linkage adjustment as outlined in the Transmission Section.
26. Replace hood assembly, aligning previously scribed marks.

There are three optional V-8 engines available for the 1956 Chevrolet passenger cars. The displacement for each of these engines is 265 cubic inches. All engines for 1956 are equipped with hydraulic lifters.

The standard or overdrive transmission equipped V-8 engine develops 162 horsepower at 4200 RPM. On Powerglide transmission models the engine develops 170 horsepower at 4400 RPM Both engines have a compression ratio of 8.0 to 1. The major mechanical difference between the two engines is the use of a high lift camshaft in the Powerglide equipped models.

The third engine option, available for all types of transmissions, is the Super Turbo Fire V-8. This engine is equipped with a high lift camshaft, high compression cylinder heads, four barrel carburetor and a dual exhaust system. This engine develops 205 horsepower at 4600 RPM. The compression ratio is 9.25 to 1. The Super Turbo Fire V-8 is designed to obtain the utmost in performance and maintain traditional Chevrolet economy.

Cylinder Block

The basic unit of the engine, the cylinder block, is of extremely rigid construction of cast alloy iron. It provides full-length water jackets completely surrounding each of the cylinders. A cylinders are numbered 1, 3, 5 and 7 on the left bank starting from the front, and 2, 4; 6 and 8 on the right bank. This arrangement gives a consecutive order of 1 through 8 to the connecting rods. Nestled in the center of the "V" are three oil gallerys, one main gallery and two valve lifter galleries. From the main gallery, passages are drilled to provide positive pressure lubrication to the crankshaft and camshaft bearings (fig. 60).

Cylinder Heads

The cylinder heads are of cast alloy iron and provide combustion chambers that give the engine its 8.0 to 1 compression ratio. Oil return holes in the heads allow valve rocker mechanism lubricant to drain back into the crankcase. A new valve rocker arrangement is utilized to provide long, trouble-free life. Each valve has a rocker arm, pivoted with a ball-stud arrangement that allows rapid clearance adjustment.

Each rocker arm and valve are lubricated by oil delivered through hollow valve push rods.

On standard shift models, a passage in each lifter allows oil from the lifter oil gallery to pass into the push rod at its seat and travel up the rod to lubricate the valve mechanism. Powerglide equipped models have a higher oil pressure in the lifter gallery, made available by a larger groove in the rear camshaft bearing which feeds the gallery. An inertia-type valve in the hydraulic lifter opens twice during each valve cycle, allowing the oil to pass into the push rod.

Cylinder heads are interchangeable from left to right bank.

Manifolds

The manifolds of the V-8 engine are designed for optimum economy and performance through a free-breathing design. The intake manifold, (fig. 61) fitted with a two-barrel carburetor, is bolted to both cylinder heads, and is in the center of the "V." Two exhaust manifolds are utilized to carry exhaust gases from the cylinder heads, each bolted to its mating cylinder head on the outside of the "V." An exhaust crossover pipe, underneath the engine, connects the two exhaust manifolds to a common low back pressure exhaust system. An exhaust gas passage through the intake manifold casting allows exhaust gases to preheat the manifold under warm-up and low-speed operating conditions. A thermostatically controlled valve on the right bank exhaust pipe controls the addition of heat to the intake manifold.

Crankshaft

The crankshaft, of forged alloy steel, is supported on five precision-interchangeable insert type bearings. The counterbalance weights are machined to provide clearance and aid in maintaining engine balance. An inertia-type, rubber mounted harmonic balancer is fitted to the front of the crankshaft along with the crankshaft timing chain sprocket. A cast iron flywheel is bolted to the rear of the crankshaft for standard shift models. On Powerglide models, a slotted pressed metal flywheel is utilized. The starter ring gear is welded to the outside diameter of the flywheel. Crankshaft oil sealing is accomplished by an oil slinger and a spring-loaded neoprene seal at the front and a graphite wick type seal at the rear. Drilled oil passages provide pressure lubrication for the connecting rod journal bearings.

Camshaft

The high-lift, cast iron camshaft is mounted in the center of the "V" on babbit type bearings. It is chain driven from the crankshaft through a silent link type chain. The camshaft bearings have a full-pressure type of lubrication.

Camshaft Bearings

On six cylinder engines camshaft bearing removal and installation is accomplished in one operation with tool numbered J-6356. This tool has adapters to fit all six cylinder engines from 1937 to 1956. With this tool, the front two bearings are replaced first, then the rear two bearings are replaced. The tool has been engineered for the precision type camshaft bearings used in all 6 Cylinder Chevrolet Engines.

Replacement

1. With camshaft removed, drive out expansion plug from cylinder block at the rear of the rear camshaft bearing, by driving it out from the inside.
2. Install a bearing Replacer in first and second camshaft bearing with new bearing installed on trailing edge of each Replacer. Trailing edge of Replacer should be towards center of engine.
3. Assemble tool with nut and washer on rear of screw shaft.
4. Index assembled tool through camshaft bearing Replacer in number 2 bearing, then turn nut on screwshaft to end of threads. While turning nut on screwshaft, install washer on front of shaft and feed screwshaft through Replacer in number 1 bearing.
5. Install bracket and thrust bearing on front of screwshaft and install remaining nut on screwshaft. Tighten nut until all threads are engaged.
6. Tighten nut behind number 1 bearing Replacer snugly. Repeat operation for number 2 Replacer.
7. Using two wrenches, hold screwshaft with one wrench while turning the front nut with the other. Pull new bearing into place, washer will act as bearing stop. CAUTION: Align oil holes in bearings with oil holes in block before putting into place.
8. Disassemble tool and repeat operation for rear two camshaft bearings.

Pistons and Connecting Rods

Aluminum alloy pistons are used in the V-8 engine with forged steel connecting rods. The hardened and ground piston pins are mounted off center and are a tight press fit in the connecting rods and pivot in the pistons. Two cast iron twist type compression rings are used. The top ring is chrome-flashed for long life. The oil control ring is of the steel rail type with a crimped flat spring steel expander.

A squirt hole in each connecting rod lubricates the cylinder walls.

Valve Lifters

Fixed-length cast iron valve lifters are used m engines equipped with standard shift transmissions. On Powerglide engines, hydraulic valve lifters (fig. 62) are utilized to provide maximum power and minimize valve train noise.

The hydraulic valve lifter consists of the heat treated alloy cast iron valve lifter body, plunger, plunger spring, ball check valve, ball check valve retainer, push rod seat, push rod seat retainer ring, inertia valve and valve retainer.

A direct oil feed from the main oil gallery line to the valve lifters is maintained at all times. This oil feed indexes with oil holes in the lifter body. Oil holes in the plunger index with the holes in the lifter body to pick up oil transmitted from the oil gallery.

Whenever lash tends to be present, the plunger spring expands, pushing the plunger until solid contact is made with the push rod and linkage. This creates a difference in oil pressure on either side of the ball check valve, the lower oil pressure being below the plunger. The higher pressure above forces the ball check valve away from the seat and allows the oil to flow below the plunger to fill the lower cavity with oil until the pressure is equalized.

When the lifter is raised by the cam, the increased oil pressure below the plunger forces the ball check valve on its seat, and the lifter then becomes a hydraulic ram, effectively a solid connecting link.

There is a controlled amount of oil leakage between the plunger and valve lifter body while the engine valve is open to eliminate the possibility of a "negative valve lash clearance" condition as the engine components change size during warm-up.

Engine Supports

The engine is supported at the front by two strut type rubber engine mounts (fig. 63). At the rear of the engine, two shear type rubber mounts support the engine at the clutch or converter housing.

Engine Accessories

The other engine components such as distributor, fuel pump, generator, etc., discussed in other sections of this manual.

Engine or under hood maintenance is divided into three categories, routine inspection, periodic maintenance and tune-up. Each category serves to insure the maximum in performance, economy and long life built in to the Chevrolet engines.

ROUTINE INSPECTION

The routine inspection operations are those items which should be checked at regular intervals, determined by the service condition of the vehicle and varying from daily to semimonthly. The engine oil level should be maintained between the "Full" and "Add" marks on the dipstick. The battery electrolyte level should be maintained at the bottom of the split rings in the battery filler openings, by the addition of distilled or de-mineralized water. The cooling system fluid level should be maintained one inch below the bottom of the filler neck of the radiator with a cold cooling system, or at the bottom of the filler neck when the system is warm. These three checks are important to prevent damage to the battery and engine and should be made as frequently as driving conditions demand.

PERIODIC MAINTENANCE

The periodic maintenance includes those items requiring service at the regular 1000 mile lubrication operations. As called out in the Lubrication Section of this manual, these items are the starter solenoid, generator and distributor. In addition, an engine crankcase oil change and air cleaner element and breather cap cleaning is recommended every 2000 to 3000 miles as discussed in the Lubrication Section of this manual.

Engine Tune-Up

One of the most important duties to perform on modern high compression engines is proper engine tune-up. This operation, more than any other, determines whether or not the vehicle will produce the maximum performance with the greatest economy. Only by performing these operations and staying within limits, clearances and specifications, is it possible to obtain the performance and economy built into the Chevrolet engine.

Tune-up operations should follow a definite procedure. A process of elimination by checking each individual component one by one is costly and time consuming. A fast, high-quality tune-up can be performed, using a group of test instruments designed specifically for tune-up work. By combining tune-up operations with testing operations, only the necessary items need be serviced and top performance will be assured with a minimum of time and cost.

Before making any checks on an engine, it should be run for several minutes and allowed to warm up and normalize. This assures proper lubricant viscosity at each engine component and that engine components will be at their operating temperature and size. In each of the following tests and operations, a visual inspection should always be made for unusual or out-of-line conditions.

Cranking Voltage Test

The cranking voltage test checks the starting mechanism and circuit as well as the ignition primary circuit to the coil and will check to see that the ballast resistor is being shorted out during cranking.

1. Connect a voltmeter of approximately 16 volts capacity with the positive lead to the positive or battery terminal of the ignition coil and the negative lead to a good ground.
2. Remove coil wire from distributor cap.
3. Turn ignition switch to "On" position, note meter reading and then turn switch to "Start" position. Crank engine for 15 seconds and read voltmeter while still cranking. With the switch in the "On" position, the meter should indicate 5 to 7 volts. If it does not, refer to the Engine Electrical Section of this manual for further checks.

With the switch in the "Start" position and the engine cranking, the meter should read 9.0 volts or better with a good rate of cranking speed. If the reading is below 9.0 volts or the engine cranks slowly, further tests must be made to determine the cause. The Engine Electrical Section of this manual outlines the battery testing, starter circuit testing and ignition primary circuit testing procedures.

Battery Hydrometer Test

In normal operation, a charging system in good condition should maintain the battery in at least a 3/4 charge condition. A hydrometer test should show a specific gravity of at least 1.215 or better and a maximum variation between cells of 0.025 gravity points. If either of these two specifications are not met, the battery and charging system should be thoroughly checked and tested as outlined in the Engine Electrical Section of this manual.

After the hydrometer check, the electrolyte level should be brought up to the bottom of the split-rings in the filler openings. If there is evidence of acid, dirt or resultant corrosion on the top of the battery, the top should be cleaned with ammonia or soda water and flushed with water. Exercise care not to get solution in the filler holes through vent holes. If the terminals show corrosion, they should be removed and the terminal and posts thoroughly cleaned. The posts and terminals should be completely coated with petrolatum and then reassembled and tightened securely.

Compression

The compression of each cylinder should be checked, because an engine with uneven compression cannot be tuned successfully to give peak performance.

1. Remove any foreign matter from around the spark plugs, and then loosen them about one turn to break free any accumulation of carbon.
2. Start engine and accelerate to 1000 RPM to blow out the carbon. (Starting and accelerating the engine after the plugs are loosened is extremely important in preventing false compression readings due to chips of carbon being lodged under, the valves.)
3. Stop engine and remove spark plugs, placing them in order that they were removed.
4. Block throttle in wide open position.
5. Insert compression tester in a spark plug hole (fig. 64).
6. Crank engine with the starting motor until the cylinder being tested passes through at least four compression strokes, using the same number of strokes on each cylinder.
7. Repeat this test on all cylinders and record the compression reading of each cylinder.
8. Compression on all cylinders should be 130 psi or better and all cylinders should read alike within 10 psi for satisfactory engine performance.

Should a low compression reading be obtained on two adjacent cylinders, it indicates the possibility of a leak from one cylinder to the other, usually caused by a leak at the cylinder head gasket. If the compression readings are low, or vary widely, the cause of the trouble may be determined by injecting engine oil on top of the pistons of the low reading cylinders. Crank the engine over several times, then take a second compression test. If there is practically no difference in the readings when compared with the first test, it indicates sticky or poorly seating valves. However, if the compression on the low reading cylinders is higher and about uniform with the other cylinders, it indicates compression loss past the pistons and rings. The cause of low or uneven compression should be corrected before proceeding with an engine tune-up.

Spark Plugs

Spark plug life is governed to a large extent by operating conditions. To insure peak performance, spark plugs should be checked and tested frequently and replaced as necessary.

The spark plugs used as standard equipment on all Chevrolet Passenger Engines are AC 44-5 If plug fouling is being experienced in a vehicle because of continuous low-speed operation, AC 46-5 plugs are available to combat this situation. If Excessive electrode wear is being experienced in a vehicle because of continuous high speed driving or heavy-duty operation, AC 43-5 COM plugs are available for better spark plug life.

Plugs with wide gaps or dirty plugs may give satisfactory operation at idling speed, but under operating conditions may break down. Faulty plugs are evident in a number of ways such as, wasting gasoline (in extreme cases one gallon in every ten), power loss, loss of speed, hard starting and general poor engine performance.

Dirty or leaded plugs may be evident by black carbon deposits, or red, brown, yellow or blistered oxide deposits on the plugs. The black deposits are usually the result of slow speed driving and short runs, where sufficient engine operating temperature is seldom reached. Worn pistons, rings, faulty ignition, over-rich carburetion and spark plugs which are too "cold" will also result in carbon deposits. These oxide deposits, a consequence of the use of leaded fuel, usually result in spark plug failure under severe operating conditions. The oxides have no adverse effect on plug operation as long as they remain in a powdery state. But, under high speed or hard pull, the powder oxide deposits melt and form a heavy glaze coating on the insulator. When hot, this coating acts as a good electrical conductor, allowing current to follow the deposits and short out the plug.

Excessive gap erosion on plugs of low mileage, usually indicates the engine is operating at speeds or loads that are consistently greater than normal or that a plug which is too "hot" is being used. In addition, electrode wear may be the result of plug overheating, caused by combustion gases leaking past the threads and gaskets, due to insufficient compression of the spark plug gaskets, or dirt under the gasket seat. Too-lean carburetion will also result in excessive electrode wear.

Broken upper insulators usually result from a poor fitting wrench or an outside blow. The cracked insulator may not make itself evident immediately, but will as soon as oil or moisture penetrates the fracture. The fracture is usually just below the crimped part of the shell and may not be visible.

Broken lower insulators usually result from carelessness when regapping and generally are visible. In fairly rare instances, this type of a break may result from the plug operating too "hot" such as encountered in sustained periods of high speed operation or under extremely heavy loads. When regapping a spark plug, to avoid lower insulator breakage, always make the gap adjustment by bending the ground or side electrode. Never bend the center wire. Spark plugs with broken insulators should always be replaced.

Clean the spark plugs thoroughly, using an abrasive-type cleaner. If the porcelains are badly glazed or blistered the spark plugs should be replaced. All spark plugs must be of the same make and number or heat range. Use a round feeler gauge to adjust the spark plug gaps to .0351". Install the spark plugs in the engine with new gaskets and tighten to 20-25 ft. lbs. torque. If torque wrench is not available, tighten plugs finger tight and 1/2 turn more.

Air Cleaner

1. Remove cover wing nut, cover and filter element.
2. Wash filter element thoroughly in cleaning solvent.
3. Let element dry and dip in engine oil and allow excess oil to drain.
4. Install element and cover and secure with wing nut. NOTE: If oil bath air Cleaner is used, see instructions under Engine-Fuel.

Manifold Heat Valve

Check valve shaft to make sure it is free. If shaft is sticking, free it up with kerosene or alcohol containing a small amount of baking soda (fig. 65).

Ignition Distributor

1. Visually check the spark plug wires for damaged insulation, oil soaked condition and proper installation. The numbers formed on the rubber support grommets indicate proper position for the wires.
2. Remove the distributor cap. Check the cap and distributor rotor for Cracks or carbon tracks and burned or pitted contacts.
3. Check the distributor automatic advance mechanism by turning the distributor cam in a clockwise direction as far as possible. Release the cam and see if the springs return it to its retarded position. If the cam does not return readily, the distributor must be disassembled and the cause of the trouble corrected. See Engine Electrical Section for Distributor Repair.
4. Check to see that the vacuum spark control operates freely by turning the breaker plate counterclockwise and see that the spring returns it to the retarded position. Any stiffness in the operation of the vacuum spark control will affect the ignition timing.
5. Examine the distributor points. Dirty points should be cleaned with a clean point file. Normal point condition is an overall gray color. If a test instrument for checking resistance is available, check the point resistance. The judgment of point quality should be a combination of visual inspection and a resistance or voltage drop check. If points are badly pitted, obviously worn or seriously misaligned, replacement is recommended. If, with the points closed and the ignition switch in the "On" position, there is less than 0.125 voltage drop across the points, the points may be considered satisfactory for further use. This check may be made with a sensitive voltmeter or with the various point resistance meters on the market. For point replacement procedure, see the Engine Electrical Section in this manual.
6. Check the contact point alignment and align the points if they have been cleaned or replaced. Align by bending the stationary point only.
7. Crank the engine until the cam follower is located between the cams. Hook the end of a distributor point scale over the movable point and pull steadily on the spring scale until the points just start to open. At this point the reading on the scale should be between 17-21 ounces. Adjust the tension by bending the breaker arm spring as required (fig. 66).
8. Crank the engine until the distributor point cam follower rests on the peak of the cam. Adjust the point gap to .016" for old points, .019" for new points, using a feeler gauge or .dial indicator. This operation must be performed very accurately because it affects point dwell or length of time the points remain closed in operation and, in turn, ignition coil performance. NOTE: The standard point setting is .016". When new points are installed, adjust points to .019' as the cam follower will wear down slightly while seating to the cam.
9. If a dwell or cam angle meter is available, start the engine and check the dwell, which should be 26° to 33°. If the cam angle or dwell is outside the specified limits, recheck gap and check for defective or misaligned points, or worn distributor cam lobes. Proper point gap should produce a dwell angle within the specified limits.
10. If a dwell or cam angle meter is available, note dwell variation between idle and 1750 engine RPM. This should not exceed 3°. Excessive variation indicates wear in the distributor. NOTE: Do not make dwell or cam angle readings above 1750 engine RPM.

Ignition Timing

1. Attach a timing light to the No. 1 spark plug and spark plug wire, using an extension to make contact, and to a good ground. Disconnect vacuum advance, start engine and run at 1000 R.P.M. with light aimed at top left of harmonic balancer.
2. Loosen distributor clamp and rotate distributor body until the mark on the harmonic balancer lines up with the 8 BUDC mark on the timing tab welded to the front end cover. This is 4 marks toward the center of the vehicle from the "0" mark (fig. 67).
3. Tighten distributor clamp screw, remove timing light, connect vacuum advance and reset engine idle.

Ignition Performance

If ignition performance test equipment is available, the ignition system performance should be tested in accordance with the equipment manufacturers procedures. If such equipment is not available, the ignition coil and distributor condenser should be checked on available equipment, and the ignition circuit wiring and terminals thoroughly inspected.

Carburetor-Inspection and Idle Adjustment

1. Inspect carburetor for loose body screws, damaged linkage, loose mounting, fuel leaks or excessive dirt accumulations.
2. Start and operate engine for a sufficient period of time for engine to reach normal operating temperature.
3. Set idling speed by adjusting stop screw on carburetor throttle lever. 450-500 RPM with Standard Transmission 400-450 RPM with Powerglide Transmission in Drive Range.
4. Turn idle mixture screws gradually to right or left to give peak RPM and highest steady reading on vacuum gauge.
5. If engine idles too fast after this adjustment, readjust throttle stop screw until correct idle speed is obtained. Recheck idle mixture adjustment. If any fault was found during visual inspection or it is impossible to obtain proper idle adjustment, remove carburetor from engine, disassemble, clean, inspect and reassemble carburetor as outlined in Engine-Fuel Section. Install carburetor and repeat. idle adjustment.

Valve Adjustment

With the engine warmed up and normalized, torque the cylinder head and manifold bolts as outlined under Cylinder Head Service Operations in this section. Head Bolt Wrench Adapter J-5860 may be used with various extensions to reach head bolts. On models equipped with standard or overdrive transmission, adjust the valves as outlined under Cylinder Head Service Operations in this section. Correct valve lash is .008" on intake valves, .016" on exhaust valves. On models equipped with Powerglide transmission, valve adjustment is not normally required as a tune-up operation.

Cooling System

1. Check all hoses and connections for evidence of leakage or decay. Make certain that the spring-type clamps are positioned squarely on the hoses and are over the pipe or casting that the hose is attached to.
2. Check the coolant level in the radiator, level with bottom of filler neck with a warm engine.
3. Check the fan belt condition and adjustment and adjust if necessary. Correct adjustment will produce 13/16" deflection with a light force applied midway between the fan pulley and generator pulley (fig. 68).

Operating Voltage

The operating voltage test serves as a check on the charging system in general. If the findings are not within limits, the entire charging system check should be made as outlined in the Engine Electrical Section of this manual before changes are attempted.

1. Attach voltmeter leads to the battery terminal of the voltage regulator and ground.
2. Attach a tachometer to measure engine speed.
3. With a normalized engine and regulator, start engine and run at 1750 RPM.
4. When voltmeter needle stabilizes, note reading. The reading should normally be 14.0 to 15.0 volts. The reading should be correlated with the battery hydrometer check and electrolyte level check if over-charging or undercharging is suspected. See the Engine Electrical Section of this manual for a more complete discussion on voltage regulator settings and charging system checks.

Road Test

After the completion of the tune-up, the vehicle should be road tested to check out the job and add insurance to the value of the tune-up.

Cylinder Head and Valve Mechanism

Valve Adjustment

Before adjusting valve stem to rocker arm clearance it is extremely important that the engine be thoroughly warmed up to normalize the expansion of all parts. This is very important because during the warm-up period, the valve clearances will change considerably. To adjust the valves during or before this warm-up period will produce clearances which will be far from correct after the engine reaches normal operating temperature. Tests have shown that valve clearances will vary as much as .005" from a cold check through the normalizing range.

Covering the radiator will not materially hasten this normalizing process because even with the water temperature quickly raised, it does not change the rate at which the oil temperature increases and becomes stabilized, or the engine parts become normalized.

The actual temperature of the oil is not as important as stabilizing the oil temperature. The expansion or contraction of the valve mechanism, cylinder head and cylinder block are relative to this oil temperature. These parts stop expanding and valve clearance changes cease to take place only after the oil temperature is stabilized.

1. Normalize engine.
2. Remove automatic choke heat tube and remove rocker arm covers. Keep cover screws and reinforcements together.
3. Check torque of all manifold bolts and torque cylinder head bolts as outlined under Cylinder Head Installation. NOTE: Correct torque for cylinder head bolts is 60 to 70 ft. lbs., exhaust manifold bolts, 25 to 35 ft. lbs., and intake manifold bolts, 25 to 35 ft. lbs.
4. Install automatic choke heat tube.
5. Lubricate valve stems to assure freedom of action.
6. On models equipped with solid lifters; Adjust valve rocker arm clearance with the engine normalized and idling by turning the self-locking rocker arm stud nuts as required to obtain .008" clearance on intake valves, and .016" clearance on exhaust valves (fig. 69). On models equipped with hydraulic lifters;
   • Crank engine until mark on harmonic balancer lines up with center or "0" mark on the timing tab fastened to the crankcase front end cover, with the engine in the Number 1 firing position. This may be determined by placing fingers on the number 1 cylinder valves as the mark on the balancer comes near the "0" mark on the front end cover. If the valves are not moving, the engine is in the number 1 firing position. If the valves move as the mark comes up to the timing tab, the engine is in number 6 firing position and should be turned over one more time to reach the number 1 position.
   • Valve adjustment is made by backing off the adjusting nut (rocker arm stud nut) until there is play in the valve push rod and then tightened to just remove all push rod to rocker arm clearance. This may be determined by rocking push rod as the nut is tightened. When rod does not readily move in relation to the rocker arm, the clearance has been eliminated. The adjusting nut should then be tightened an additional 3/4 turn to place the hydraulic lifter plunger in the center of its travel. No further adjustment is required.
   • With the engine in the number 1 firing position as determined above, the following valves may be adjusted. Exhaust-1,3,4,8 Intake-1,2,5,7
   • Crank the engine one revolution until the pointer "0" mark and harmonic balancer mark are again in alignment. This is number 6 firing position. With the engine in this position, the following valves may be adjusted. Exhaust-2,5,6,7 Intake-3,4,6,8
7. Remove automatic choke heat tube.
8. Install rocker arm covers, using new gaskets, and tighten screws to 2 1/2 ft. lbs., after determining that cover hole reinforcements are in place.
9. Install automatic choke heat tube, start engine and check for oil leaks at rocker arm covers.

The hydraulic valve lifters used in models having the Powerglide engine very seldom require attention. The lifters are extremely simple in design, readjustments are not necessary, and servicing of the lifters require only that care and cleanliness be exercised in the handling of parts.

The easiest method for locating a noisy valve lifter is by use of a piece of garden hose approximately four feet in length. Place one end of the hose near the end of each intake and exhaust valve with the other end of the hose to the ear.

In this manner, the sound is localized making it easy to determine which lifter is at fault.

Another method is to place a finger on the face of the valve spring retainer. If the lifter is not functioning properly, a distinct shock will be felt when the valve returns to its seat.

The general types of valve lifter noise are as follows:

1. Hard Rapping Noise-Usually caused by the plunger becoming tight in the bore of the lifter body to such an extent that the return spring can no longer push the plunger back up to working position. Probable causes are:
   • Excessive varnish or carbon deposit causing abnormal stickiness.
   • Galling or "pick-up" between plunger and bore of lifter body, usually caused by an abrasive piece of dirt or metal wedging between, plunger and lifter body.
2. Moderate Rapping Noise Probable causes are:
   • Excessively high leakdown rate.
   • Leaky check valve seat.
3. General Noise throughout the Train-This will in almost all cases, be a definite indication of insufficient oil supply.
4. Intermittent Clicking Probable causes are:
   • A microscopic piece of dirt momentarily caught between ball seat and check valve ball.
   • In rare cases, the ball itself may be out-of-round-round or have a flat spot.

In most cases where noise exists in one or more lifters, all lifter units should be removed, cleaned in a solvent, reassembled, and reinstalled in the engine. If dirt, varnish, carbon, etc. is shown to exist in one unit, it more than likely exists in all the units, thus it would only be a matter of time before all the lifters caused trouble.

In instances where parts are damaged, particularly the plunger or lifter body, the complete lifter unit should be replaced. However, in rare or emergency cases an Arkansas hard stone may be used to remove metal scratches or humps; and if after correcting, the plunger will operate freely in the lifter body, the parts may be thoroughly cleaned and the unit assembled and installed.

A few precautions to follow when servicing the valve lifters are:

1. Plungers are not interchangeable, they are a selective fit at the factory. Should a plunger or lifter body become damaged, it is necessary to replace the whole unit.
2. The plunger must be free in the lifter body. A simple test for this is to be sure the plunger will drop of its own weight in the body.
3. There must be no excessive leakdown and there must be no ball check valve leakage.

RemovaI

1. Remove rocker arm cover attaching screws with reinforcements and remove covers and gaskets.
2. Remove intake manifold as described under Cylinder Head Reconditioning in this section.
3. Back off rocker arm nuts until arms may be pivoted away from push rods. Remove push rods.
4. Remove hydraulic valve lifters.

NOTE: Valve litters should be placed in a rack in their proper sequence so they can be installed in their same positions in the cylinder block.

Disassembly and Assembly

1. Hold plunger down with a push rod and, using a small screwdriver or awl, remove plunger retainer.
2. Remove push rod seat, plunger, ball check valve, ball retainer and spring. Figure 70 shows a layout of the parts.
3. Thoroughly clean all parts in cleaning solvent, and inspect them carefully. If any parts are damaged, the entire lifter assembly should be replaced. The inertia valve in the plunger for rocker arm lubrication should move when the plunger is shaken.
4. To reassemble, invert the plunger and set the ball into hole in plunger and place the ball check valve retainer over the ball and on the plunger.
5. Place check valve retainer spring over retainer.
6. Assemble valve lifter body over the complete assembly.
7. Turn assembly over, and install push rod seat. Compress plunger with push rod and install retainer.
8. Compress plunger to open oil holes and fill plunger with SAE 10 oil. Work plunger up and down and refill.

Installation

1. Install valve lifters.
2. Install intake manifold as described under Cylinder Head Reconditioning in this section.
3. Install push rods.
4. Pivot rocker arms to engage push rods and adjust valves.

Adjustment

See Valve Adjustment in this section.

The condition of the cylinder heads and valve mechanism, more than anything else, determines the. power, performance and economy of a valve-in-head engine. Extreme care should be exercised when conditioning the cylinder heads and valves to maintain correct valve stem to guide clearance, correctly ground valves, valve seats of correct width and correct valve adjustment.

Removal

1. Drain radiator, remove air cleaner wing nut and remove air cleaner.
2. Disconnect throttle rod from carburetor. On Powerglide models, disconnect lower transmission throttle lever rod from bellcrank mounted on coil bracket.
3. Disconnect fuel, vacuum and automatic choke lines from carburetor.
4. Disconnect coil primary wires. Disconnect coil to distributor secondary wire. Remove distributor clamp and remove distributor.
5. On over-drive equipped models, disconnect kick-down switch wires from switch.
6. Remove spark plug wires from spark plugs and remove plugs.
7. Remove water outlet hose and heater hose, if so equipped, from intake manifold.
8. Remove, temperature indicator unit from intake manifold.
9. Remove bolts attaching intake manifold to cylinder heads. Remove manifold.
10. Remove fan belt.
11. Remove exhaust manifold to exhaust crossover pipe stud nuts and allow cross-over pipe to drop for clearance. Remove exhaust manifold heat control valve from right bank exhaust manifold.
12. Disconnect generator field and armature wires from generator.
13. Remove exhaust manifold to cylinder head bolts and remove exhaust manifolds.
14. Remove choke heat tube and remove rocker arm covers.
15. Back off rocker arm nuts, pivot rocker arms to clear push rods and remove push rods. Be certain that push rod seats on solid lifters do not come out of lifters with push rods. Snap push rod lower end to one side before lifting, to break the push rod loose from the seat.
16. Remove cylinder head bolts, cylinder heads and gaskets.

Disassembly

1. Place cylinder head assembly on its side on a bench and, using Valve Spring Compressor Tool KMO-642, compress valve spring and remove valve locks. Release tool and remove spring retainer, valve baffle, and seal from stem. Repeat this operation on each valve (fig. 71).
2. Remove valves from bottom of cylinder head and keep them in their proper sequence for inspection and assembly.
3. Remove rocker arm nuts, lift rocker arms off studs and remove pivots from rocker arms.

Cleaning

1. Clean all carbon from combustion chambers and valve ports using Carbon Removing Brush KMO-7004 (fig. 72).
2. Thoroughly clean the valve bores, using Valve Bore Cleaner KMO-122 (fig. 73).
3. Clean all deposits from hollow push rods, inside and outside; disassemble, clean and reassemble all valve lifters.
4. Clean valve stems and heads on a buffing wheel.
5. Clean carbon deposits from pistons and cylinders.
6. Wash all parts in cleaning solvent and -dry them thoroughly.

Inspection

1. Inspect the cylinder heads for cracks in the exhaust ports, combustion chambers, or external cracks to the water chamber.
2. Inspect the valves for burned heads, cracked faces or damaged stems.
3. Check fit of valve stems in their respective bores. NOTE: Excessive valve to bore clearance may cause lack of power, oil consumption, rough idling and noisy valves. Insufficient clearance will result in noisy and sticky functioning of the valve and disturb engine smoothness of operation.
   • Intake valve stem to bore clearance should be .001" to .003" while exhaust stem clearance should be .002" to .004". Valve stem clearance may be accurately determined by use of a Last Word Indicator. Clamp the indicator on one of the valve rocker studs, arranging the indicator so that movement of the valve stem from side to side (crosswise to the head) will cause a direct movement of the indicator stem. The indicator stem must contact the side of the valve stem just above the cylinder head. With the valve head dropped about 1/16" Off the valve seat, move the stem of the valve from side to side with light pressure to obtain the clearance. By trying new valves in the old bores it can be determined whether the valves should be replaced, or the bores reamed and oversize valves installed.
4. Check valve spring tension with KMO-607 Spring Tester (fig. 74). NOTE: Spring should be compressed to 1 45/64", at which height it should check from 71 to 79 pounds. Weak springs affect power and economy and should be replaced if not within the above limits.
5. Check valve lifters for free fit in block. The end that contacts the camshaft should be smooth. If this surface is worn or rough, the lifter should be replaced.
6. Check push rods for bent condition.

Repairs

Valve Bores

Valves with oversize stems are available in the following sizes, .003", .015" and .030". Reamer set J-5830 may be used to ream the bores for new valves (fig. 75).

Rocker Arm Studs

Rocker arm studs that have damaged threads may be replaced with standard studs. If the studs are loose in the head, oversize studs, available in .003" oversize, may be installed after reaming the holes with J-5715 reamer set.

1. Remove old stud by placing spacer J-5802 over the stud, installing nut and flat washer and removing stud by turning nut (fig. 76).
2. Ream hole for oversize stud, using Reamer J-5715 (fig. 77)
3. Coat press-fit area of stud with hypoid axle lubricant. Install new stud, using tool J-5801 as a guide. Gauge should bottom on head (fig. 78).

Reseating Valve Seats

Reconditioning the valve seats is very important, because the seating of the valves must be perfect for the engine to deliver the power and performance built into it. Another important factor is the cooling of the valve heads. Good contact between each valve and its seat in the head is imperative to insure that the heat in the valve head will be properly carried away.

Several different types of equipment are available for resealing valve seats; the recommendations of the manufacturer of the equipment being used should be carefully followed to attain proper results.

Regardless of the methods used for seat repair, the final seat for the valves should be 3/64" to 1/16" for intake seats and 1/16" to 3/32" for exhaust seats. The seats should be concentric within .002" indicator reading (fig. 79). Seats should be 46.

Refacing Valves

Valves that are pitted can be refaced to the proper angle, insuring correct relation between the head and stem on a valve refacing machine. Valve stems which show excessive wear, or valves that are warped excessively should be replaced. When a valve head which is warped excessively is refaced, a knife edge will be ground on part or all of the valve head due to the amount of metal that must be removed to completely reface. Knife edges lead to premature breakage, burning and preignition due to heat localizing on this knife edge. If the edge of the valve head is less than 1/32" thick after grinding, replace the valve. All valves should be ground to 45°. Follow the grinding equipment manufacturers procedures for use of the equipment.

Assembly

1. Clean valves, valve seats, valve bores and cylinder heads thoroughly.
2. Insert the valve in the port and set the valve spring in place with close coiled end of spring against cylinder head and, on intake valves, install baffle in spring.
3. Place cap in position on spring or baffle and compress the spring with Compressor Tool KMO-642 (fig. 71).
4. Install oil seal in lower groove on stem making sure seal is flat and not twisted in groove. Install valve locks and release compressor tool, making sure locks seat properly in upper groove on stem.
5. Assemble the remaining valves, valve springs, spring caps, baffles, oil seals and valve locks in the cylinder heads in the same manner.
6. Check the installed height of the valve springs. Reseating valves raises the installed height of the springs and, if excessive, will have the effect of weak valve springs. Use a narrow, thin scale and measure from the spring seat in the head to the top of the valve spring. If this is found in excess of 1 47/64", install a valve spring seat shim, approximately 1/16" thick. At no time should the spring be shimmed to give an installed height of less than 1 11/16".

NOTE: If springs are to be changed with cylinder head installed, J-5892 Spring Compressor may be used to compress springs for removal or installation. Compressed air or a screwdriver may be used to hold the valves in place, used through the spark plug hole.

Installation

1. Thoroughly clean out cylinder head bolt holes in the block and clean cylinder bolt threads. Then place new cylinder head gaskets in position on cylinder block. Use a good head gasket paste with these steel gaskets.
2. Place the cylinder heads in position over the two dowel pins in the block.
3. Oil the threads of all long cylinder head bolts. Coat threads of all short cylinder head bolts with special sealing compound such as Permatex No. 3. These bolts protrude into the water passages and require this compound to prevent rusting.
4. Install bolts finger tight.
5. Tighten the cylinder head bolts a little at a time in the order shown (fig. 80). The final tightening should be 60-70 ft. lbs.
6. Install 16 valve lifters and 16 push rods in their respective bores.
7. Insert pivots in valve rocker arms, install rocker arms over studs, and install nuts.
8. Clean gasket faces of manifolds and cylinder heads.
9. Install intake manifold end gaskets on cylinder block. Coat ends of intake manifold side gaskets around water passages with a good gasket sealing compound and install on cylinder heads.
10. Install intake manifold and bolts. Tighten finger tight. Tighten bolts a little at a time according to the sequence shown in fig. 81. Final torque should be 25-35 ft. lbs
11. Install temperature indicator element in intake manifold.
12. Install radiator core to intake manifold hose.
13. Coat end of exhaust manifold gaskets around water passages and exhaust manifold bolts with a graphite type grease. Install exhaust manifolds and bolts. Tighten to 25-35 ft. lbs. torque.
14. Clean mating surfaces and install exhaust manifold heat control valve and exhaust cross-over pipe, using new gaskets and seals.
15. Clean all spark plugs with abrasive type cleaner, inspect for damage and set gap at .035" using a round feeler gauge.
16. Place new gaskets on plugs and install. Tighten to 20-25 ft. lbs.
17. Install distributor, distributor clamp and distributor and coil wiring. Roughly set timing, by adjusting for points just breaking with engine in number 1 firing position.
18. Connect spark plug wires to their respective terminals and install generator field and armature wires.
19. Connect throttle linkage and on overdrive models, connect kick-down switch wiring. On Powerglide models, install lower transmission throttle control rod to bellcrank at distributor coil mounting.
20. Connect gasoline, vacuum and automatic choke lines to carburetor.
21. Clean and install air cleaner.
22. Fill cooling system and check for leaks.
23. Normalize engine and re-torque cylinder head bolts.
24. Adjust valve clearances on all models. On solid lifter models, normalize engine and adjust valves as outlined under Valve Adjustment in this section.
25. Check ignition timing.

Removal

1. Raise front of vehicle and place on stand jacks.
2. Remove oil pan drain plug and drain crankcase oil.
3. Disconnect steering idler arm bracket from right hand frame side rail and drop for clearance.
4. Remove oil pan retaining bolts and screws and remove oil pan.

Installation

1. Thoroughly clean all gasket sealing surfaces.
2. Install rear oil pan seal in groove in rear main bearing cap. Tuck ends into groove openings in cylinder block.
3. Install side gaskets on pan rails, using grease as a retainer. Rear end of side gaskets lap rear end gasket. Tuck front ends of side gaskets into gap between front end cover seal groove and cylinder block.
4. Install oil pan front seal in groove in front end cover, with ends butting side gaskets.
5. Install oil pan and pan to cylinder block bolts. Tighten front and rear 5/16" bolts to 12 to 15 ft. lbs. Intermediate 1/4" bolts should be tightened to 6-9 ft. lbs.
6. Install steering idler arm bracket to right hand frame side rail and tighten attaching bolts securely.
7. Install oil drain plug and fill crankcase with 4 quarts engine oil.
8. Lower vehicle to floor, start engine and check for oil pressure and leaks.

The oil pump (fig. 82) consists of two gears and a pressure relief valve enclosed in a two-piece housing and driven from the distributor drive which in turn is driven by a helical gear on the camshaft.

The pump cover is equipped with a pressure regulator valve that limits oil pressure to approximately 35 psi.

The pump intake is of the floating type. It floats on the crankcase oil level, picking up only the cleanest oil in the sump. The pick-up point is just below the surface of the oil. A mesh screen filters out small particles of dirt and sludge which may be present. In the event that the screen becomes clogged, a valve in the center of the float will allow the pump to pick up oil, bypassing the screen.

Inasmuch as the oil pump is serviced on an exchange basis, no repair operations other than disassembly, cleaning and inspection operations are covered in this manual.

Removal and Disassembly

1. Remove oil pan.
2. Remove pump to rear main bearing cap bolt and remove pump, extension shaft and collar.
3. Disconnect pump shaft from extension by removing clip from collar.
4. Remove pump cover attaching screws, cover, idler gear and drive gear and shaft.
5. Remove floating intake screen from pipe by bending tang on float travel control and sliding float assembly off pipe.
6. Wash all parts in cleaning solvent and dry by using compressed air, if available. CAUTION: Do not disturb pick-up pipe. This pipe is located at assembly and determines float travel level.

Inspection

Should any of the following conditions be found during inspection operations it is advisable to replace pump assembly.

1. Inspect pump body for cracks or excessive wear.
2. Inspect oil pump gears for excessive wear or damage.
3. Check shaft for looseness in the housing.
4. Check inside of cover for wear that would permit oil to leak past the ends of gear.
5. Check the oil pick-up screen for damage to screen, by-pass valve or body. Check for oil in air chamber.

Assembly and Installation

1. Place drive gear and shaft in pump body.
2. Install idler gear so that smooth side of gear will be toward the cover.
3. Install cover and attaching screws. Tighten screws to 6 to 9 ft. lbs. and check to see that shaft turns freely.
4. Install pick-up screen on pipe and bend float travel control tang back in place.
5. Assemble collar end of extension shaft assembly over pump drive shaft, aligning tang of extension shaft with slot in end of pump drive shaft. Install retaining clip with flat end of clip in groove of pump drive shaft.
6. Assemble pump and extension shaft to rear main bearing cap, aligning slot on top end of extension shaft with drive tang on lower end of distributor drive shaft.
7. Install pump to rear bearing cap bolt and tighten to 45 to 50 ft. lbs.
8. Install oil pan.

Removal

1. Drain radiator and disconnect radiator hoses. On Powerglide models, disconnect oil cooler lines from radiator core.
2. Remove radiator core to core support bolts and remove radiator core. Note spacer shims removed, if any.
3. Remove fan belt, fan and pulley.
4. Install Harmonic Balancer Puller J-1287-B to harmonic balancer and turn puller screw to remove balancer from crankshaft.
5. Remove tool from balancer.

Installation

1. Coat front cover seal contact on balancer with engine oil.
2. Install two 3/8-16" x 1 1/2" cap screws to balancer to hold hub and flywheel portions together during assembly.
3. Position balancer on crankshaft, aligning the key on the crankshaft with the key way in the balancer.
4. Using Transmission Front Bearing Installer J-5590, drive balancer on crankshaft until the hub bottoms on the crankshaft timing sprocket (fig. 83).
5. Remove two capscrews from balancer.
6. Install fan pulley and fan to water pump fan hub and tighten bolts securely.
7. Install fan belt and adjust to give 13/16" deflection with a light load applied midway between the generator and fan pulleys.
8. Install radiator core and adjust to give to 5/8" to 3/4" clearance between fan and core. Install core to core support shims as required.
9. Install radiator hoses and, on Powerglide models, connect transmission oil cooler lines to radiator core.
10. Fill cooling system, start engine and check for leaks.

Removal

1. Remove harmonic balancer.
2. Remove oil pan.
3. Remove heater hose from water pump if so equipped. Remove water pump from cylinder block.
4. Remove crankcase front end cover attaching screws and remove front end cover and gaskets.

Repairs

Crankcase Front End Cover Oil Seal-Replace

1. Pry old seal out of cover from the front with a large screwdriver.
2. Install new seal so that open end of the seal is toward the inside of cover and drive it into position with Oil Seal Driver J-996 (fig. 84). CAUTION: Support cover at sealing area.

Installation

1. Make certain that cover mounting face and cylinder block front end plate face are clean and flat.
2. Make certain oil slinger is in place against crankshaft timing sprocket.
3. Coat the oil seal with light grease and, using a new cover gasket, install cover and gasket over dowel pins in cylinder block.
4. Install cover screws and tighten to 6-8 ft. lbs. torque.
5. Install oil pan.
6. Install harmonic balancer and water pump.
7. Start engine and check for leaks.

Replacement

1. Remove harmonic balancer and crankcase front end cover as previously described. Remove crankshaft oil slinger.
2. Crank engine until "0" marks on camshaft and crankshaft sprockets are in alignment. (fig. 85).
3. Remove three camshaft sprocket to camshaft bolts.
4. Remove camshaft sprocket and timing chain together. Sprocket is a light press fit on camshaft for approximately 1/8". If sprocket does not come off easily, a light blow with a plastic-faced hammer on the lower edge of the camshaft sprocket sprocket should the sprocket.
5. If crankshaft sprocket is to be replaced, remove, using J-5825, Crankshaft Gear Puller. Install new sprocket, aligning key and keyway, using J-5590, Transmission Front Bearing Installer.
6. Install timing chain on camshaft sprocket. Hold the sprocket vertical with the chain hanging below, and orient to align "0" marks on camshaft and crankshaft sprockets.
7. Align dowel in camshaft with dowel hole in camshaft sprocket and install sprocket on camshaft (fig. 86). NOTE: Do not attempt to drive cam sprocket on shaft as wash plug at rear of engine can be dislodged.
8. Draw camshaft sprocket onto camshaft, using the three mounting bolts. Tighten to 15-20 ft. lbs. torque.
9. Lubricate timing chain with engine oil.
10. Install crankcase front end cover and harmonic balancer as previously described.

Removal

1. Remove valve lifters as described under Cylinder Heads and Valve Mechanism.
2. Remove fuel pump and fuel pump push rod as described in the Engine-Fuel Section.
3. Remove grille assembly. See Front End Sheet Metal, Section 11.
4. Remove timing chain and camshaft sprocket as previously described.
5. Install two bolts, 5/16"-18 x 4" in two of camshaft bolt holes. Remove camshaft from engine (fig. 87). CAUTION: All camshaft journals are the some diameter and caution must be used in removing camshaft to avoid damage to bearing.

Inspection

The camshaft bearing journals are 1.8682"- 1.8692" in diameter. The journals should be checked with a micrometer for an out-of-round condition. If the journals exceed .001" out-of-round, the camshaft should be replaced.

The camshaft should also be checked for alignment. The best method is by use of "V" blocks and a dial indicator (fig. 88). The dial indicator will indicate the exact amount the camshaft is out of true. If it is out more than .002" dial indicator reading, the camshaft should be straightened.

Installation

1. Install two bolts in camshaft, lubricate camshaft and install camshaft in engine. Remove bolts.
2. Install timing sprocket and chain as previously described.
3. Install crankcase front end cover and harmonic balancer as previously described.
4. Install grille assembly as described in Front End Sheet Metal, Section 11.
5. Install valve lifters, valve mechanism, intake manifold and distributor as described in Cylinder Heads and Valve Mechanism.
6. Install fuel pump push rod, mounting plate and pump as described in Engine-Fuel Section.

Camshaft Bearings

Camshaft bearings can be replaced while engine is disassembled for overhaul, or without complete disassembly of the engine. To replace bearings without complete disassembly remove the camshaft and crankshaft, leaving cylinder heads attached and pistons in place. Before removing crankshaft, tape threads of connecting rod bolts to prevent damage to crankshaft. Fasten connecting rods against sides of engine so they will not be in way while replacing camshaft bearings.

Camshaft Bearing Removal

1. With camshaft removed, drive out expansion plug from cylinder block at the rear of the rear camshaft bearing, by driving it out from the inside. NOTE: This procedure is based on removal of the bearing nearest center of the engine first. With this method a minimum amount of turns is necessary to locate the Remover in position to remove next bearing.
2. Install nut on puller screw and turn to end of threads on puller screw.
3. Index pilot over screw with open end toward nut on puller screw.
4. Insert Remover with shoulder toward number three bearing, making sure a sufficient amount of threads are engaged on the puller.
5. Using two wrenches, hold screwshaft with one wrench while turning the front nut with the other wrench. After removing bearing from block, repeat operation for number two bearing.
6. Remove tool and reassemble tool to remove number four bearing from rear of engine.
7. Assemble remover on driver handle and remove front and rear bearing.

Installation

1. The number one or front camshaft bearing should be installed first. This bearing will act as a guide for the tool and center the number two and three bearing being pulled in place. Install the front bearing with bearing installer assembled to the drive handle, then drive bearing in. CAUTION: Align oil holes in bearing with oil holes in block before driving or pulling in place.
2. Install nut on puller screw and turn to end threads on puller screw.
3. Index pilot screw, with open end of pilot toward nut.
4. Index number three camshaft bearing on screw, then turn installer on screw with shoulder toward bearing making sure a sufficient amount of threads are engaged on the puller.
5. Turn nut on screw puller to exert pressure on pilot until bearing is installed.
6. Remove installer and repeat operation 4 and 5 for number two (fig. 7). and four bearing.
7. Install rear bearing (fig. 8) in same manner as number one bearing. Caution should be observed while installing rear bearing due to smaller size of oil pressure holes in rear camshaft bearing. Improper alignment of rear camshaft bearing will result in restricted oil pressure to valve train.
8. Install a new camshaft end plug in back end of the cylinder block at the rear camshaft bearing.

NOTE: Plug should be installed flush to 1/32 deep to maintain level surface on rear of cylinder block.

Main Bearings - Adjust in Vehicle

The main bearings are of the precision insert type and do not utilize shims for adjustment. If the clearances are found to he excessive, a new standard or oversize bearing insert, both upper and lower halves, will be required.

The clearance may be checked with the engine in the vehicle by the plastigage method as described under Major Service Operations. When one bearing is being checked, all of the other main bearing caps must be in place and at required torque. The inspection and end play check should also be made as outlined in the Major Service Operations Section.

Main Bearing Replacement, Engine in Vehicle

Main bearings may be replaced without removing the crankshaft.

1. Remove oil pan.
2. Remove spark plugs.
3. Remove cap on main bearing requiring replacement and remove bearing from shell.
4. Install a main bearing shell removing and installing tool in the oil hole in the crankshaft. NOTE: If such a tool is not available, a cotter pin may be bent as required to do the job.
5. Rotate the crankshaft in the direction of usual rotation (clockwise, as viewed from front of engine). This will roll upper bearing shell out of engine.
6. Oil new upper bearing shell and insert plain (un-notched) end of shell between crankshaft and block on the indented or notched side. Rotate the bearing into place.
7. Install new bearing shell in bearing cap.
8. Check bearing clearance as previously outlined.
9. Install oil pan.
10. Install spark plugs.

Sealing at the crankshaft rear bearing is made by machining the rear bearing cap and cylinder block to receive a wick type seal.

To install a new wick seal in the rear main bearing cap proceed as outlined below.

1. Remove rear bearing cap.
2. Remove old seal from groove and make sure groove is clean.
3. Insert new seal in groove with the fingers.
4. Using J-5788 Oil Seal Installer and a hammer, pound seal firmly into groove (fig. 89). Cut the small portion of the seal that protrudes from the groove flush with the surface of the bearing cap (fig. 90).
5. Replace cap.
6. If it should be necessary to replace the upper half of the seal it will be necessary to remove the engine from the chassis and remove the crankshaft as outlined under Major Service Operations in this section. The upper half of the seal may then be replaced in the manner described above.

Front and rear engine mountings are of the non-adjustable type. Because of this, service is seldom required. Broken or deteriorated mounts should be replaced immediately because of the added strain thrown on other mounts and drive line components.

Front Mounts-Replace

1. Remove top and bottom stud nuts and remove washer and cushion between each nut and the cross member or engine bracket.
2. Remove distributor cap.
3. Raise front of engine and remove studs with cushions, washers and retainers. CAUTION: Raise engine only enough for sufficient clearance. Check for interference between rear of engine and dash panel.
4. Replace necessary cushions (fig. 91).
5. On each end of studs, install washer, cushion with step and retainer.
6. Install stud and cushion assemblies and lower engine into place.
7. Install cushion and washer over each end of each stud, install nut and tighten securely.

Rear Mounts-Replace

1. Support engine weight to relieve rear mounts.
2. Remove mount attaching bolts from frame outrigger and flywheel housing or Powerglide transmission and remove support
3. Remove engine support.
4. Install new support and bolts.
5. Tighten bolts securely with normal engine weight resting on mounts (fig. 92).

Engine Removal

1. Drain cooling system, crankcase and transmission.
2. Scribe alignment marks on hood around hood hinges and remove hood from hinges.
3. Remove radiator hoses and heater hoses on models so equipped.
4. Remove radiator core support to core bolts and shims. On Powerglide models, remove and plug oil cooler lines. Remove radiator core.
5. Remove battery, battery support and battery cables.
6. Disconnect starter and generator wires, engine to body ground strap, oil pressure indicator wire at switch on block and coil primary lead at coil.
7. Remove windshield wiper motor. Remove temperature indicator element from cylinder head.
8. Remove air cleaner.
9. Remove fan blade and pulley.
10. Disconnect gasoline feed pipe from fuel pump and disconnect vacuum lines from intake manifold.
11. Remove distributor and coil.
12. Disconnect carburetor control rod from dash panel bell crank.
13. Disconnect exhaust cross-over pipe from exhaust pipe and muffler assembly.
14. Remove transmission control rods.
15. Remove clutch control bell crank and control rods on conventional transmission models. On overdrive models, disconnect overdrive wires and cables. On Powerglide models, remove oil filler tube, plug opening and disconnect oil cooler lines.
16. Disconnect speedometer cable at transmission.
17. Split rear universal joint. Remove propeller shaft.
18. Remove choke heat tube and rocker arm covers and install two eye bolts and spacers from Kit J-4536-A in cylinder head bolt holes.
19. Raise engine slightly and remove all four engine mounts. Remove the engine and transmission from the vehicle as a unit, tilting engine to clear core support.
20. Remove exhaust cross-over pipe and manifold heat control valve.

1. On all models equipped with a 3-speed transmission, proceed as follows:
   • Remove flywheel underpan and extension and bolts attaching transmission to clutch housing. Remove transmission. NOTE: Support the transmission as the last mounting bolt is removed and as it is being pulled away from the engine to prevent damage to clutch disc.
   • Remove throwout bearing from clutch fork and remove fork by forcing it forward and toward the center of the vehicle.
   • Install Clutch Pilot J-5824 to support clutch during disassembly. Loosen clutch to flywheel bolts a turn at a time (to prevent distortion of clutch cover) until the diaphram spring pressure is released (fig. 93). Remove all bolts, pilot assembly and disc.
   • Remove the flywheel and clutch housing.
2. On models equipped with a Powerglide transmission, proceed as follows:
   • Remove two upper transmission to converter housing bolts) install Lift Sling J-4262 and attach chain hoist to lift sling.
   • Remove spark plugs and wires, starting motor and flywheel housing cover.
   • Remove crankcase breather road draft tube from cylinder block.
   • Remove flywheel to converter bolts, working through bolt access hole on right side of flywheel housing. NOTE: Do not remove converter cover bolts which extend through holes in "heel.
   • Remove converter housing to flywheel housing bolts and separate transmission assembly from engine. Install Converter Assembly Holding Tool J-5384.
3. Remove generator from left bank exhaust manifold.
4. Remove exhaust manifold to cylinder head bolts and remove exhaust manifolds.
5. Install engine in stand. If KMO 682 Stand is to be used, J-4533-A Bracket Set or J-4533-5 Adapter Kit will allow engine to be mounted securely. Remove lifting hooks.
6. Disconnect fuel pump to carburetor pipe and remove fuel pump. Remove fuel pump mounting plate and fuel pump push rod from cylinder block.
7. Remove carburetor. On Powerglide models, remove transmission throttle lever.
8. Remove thermostat housing from intake manifold and remove thermostat. Remove water pump.
9. Remove intake manifold to cylinder head bolts and remove pipe clips, plug wire supports and intake manifold.
10. Remove spark plug wiring harness and spark plugs.
11. Remove rocker arm nuts, rocker arms and pivots, and remove push rods. Be certain that push rod seats on solid lifters do not come out of lifters with push rods. Snap push rod lower end to one side to break the push rod loose from the seat.
12. Remove cylinder head bolts, cylinder heads and gaskets.
13. Place each cylinder head assembly on its side on a bench then, using Valve Spring Compressor Tool KMO-642, compress valve spring and remove valve locks. Release tool and remove spring retainer, baffles on intake valves, then remove seal from stem. Repeat this operation on each valve (fig. 71).
14. Remove valves from bottom of cylinder head and keep them in their proper sequence for inspection and assembly.
15. Remove valve lifters. NOTE: Valve lifters should be placed in a rack in their proper sequence so they can be reinstalled in their some positions in the cylinder block.
16. Remove screw retaining crankcase inner ventilator body to cylinder block and remove ventilator body from cylinder block. CAUTION: Do not damage vent body.
17. Remove oil pan retaining bolts and screws and remove oil pan.
18. Install Harmonic Balancer Puller J-1287-B to harmonic balancer and turn puller screw to remove balancer from crankshaft (fig. 94). Remove tool from balancer.
19. Remove crankcase front end cover attaching screws and remove front end cover and gasket. Remove crankshaft oil slinger.
20. Remove three camshaft sprocket to camshaft bolts.
21. Remove camshaft sprocket and timing chain together. Sprocket is a light press fit on camshaft for approximately 1/8". If sprocket does not come off easily, a light blow with a plastic-faced hammer on the lower edge of the camshaft sprocket should dislodge the sprocket.
22. Remove crankshaft sprocket using J-5825, Crankshaft Gear Puller (fig. 95).
23. Install two bolts, 5/16"-18 x 4" in two of camshaft bolts holes. Remove camshaft from engine (fig. 87). CAUTION: All camshaft journals are the some diameter and caution must be used in removing camshaft to avoid damage to bearings.
24. Remove oil pump to rear main bearing cap bolt and remove pump, extension shaft and collar.
25. Disconnect pump shaft from extension by removing clip from collar.
26. Remove pump cover attaching screws, cover, idler gear and drive gear and shaft.
27. Remove floating intake screen from pipe by bending tang on float travel control and sliding float assembly off pipe. CAUTION: Do not disturb pick-up pipe. This pipe is located at assembly and determines float travel level.
28. Remove connecting rod journal bearing caps and install Shell Holding Tool J-5239-1 and 2 on studs. Push piston assemblies out of top of cylinder block (fig. 96). If piston rings strike ridge at top of cylinder, remove ridge to prevent damaging piston ring lands. NOTE: It will be necessary to turn the crankshaft slightly to disconnect some of the rods and to push them out of the cylinder.
29. Remove piston rings by expanding them and sliding them off the ends of the pistons. KMO 297-Q is available for this purpose.
30. Remove main bearing caps and lift crankshaft out of cylinder block. Lift bearing shells out of block and caps.

1. Wash all parts thoroughly in cleaning solvent.
2. Remove six oil gallery plugs located at front and rear of cylinder block. These oil passages should be thoroughly cleaned either by using compressed air or a wire brush. Plugs may easily be removed with a sharp punch or they may be drilled and pried out.
3. Clean all oil passages in the cylinder block by blowing them out with compressed air. It is good practice to blow them out separately.
4. Clean out the hollow push rods and the valve lifters. Solid type lifters should have the push rod seat removed for lifter cleaning. Hydraulic lifters should be disassembled for cleaning as described under Cylinder Heads and Valve Mechanism. 1
5. Clean carbon from piston heads, ring grooves and inside of piston head. Clean carbon from cylinder head combustion chambers and valve ports with Carbon Removing Brush KMO-7004. Clean valve guides with Valve Guide Cleaner KMO-122. Clean valve stems and heads on a buffing wheel.
6. Check the cylinder block for cracks in the cylinder walls, water jacket and main bearing webs.
7. Check the cylinder walls for taper, out-of-round or excessive ridge at top of ring travel. This should be done with a dial indicator (fig. 97). Set the gauge so that the thrust pin must be forced in about 1/4" to enter gauge in cylinder bore. Center gauge in cylinder and turn dial to "0." Carefully work gauge up and down cylinder to determine taper and turn it to different points around cylinder wall to determine the out-of-round condition.
8. Set the indicator to the standard cylinder size using a pair of micrometers. Then, by checking the cylinders, the oversize pistons required and the amount necessary to be removed from the cylinders can be determined.
9. Inspect the main bearings for wear or damage that would make replacement necessary.
10. Inspect camshaft bearings for wear or damage.
11. Inspect the camshaft for damaged cams or bearing journals. If the journals are out-of-round more than .001" the shaft should be replaced. Check the fit of the camshaft in the bearings. Check the camshaft for run out as described under Care, Maintenance and Adjustments.
12. Inspect the crankshaft journals and crank pins for roughness and scores. Check them with a micrometer for out-of-round or taper. If out-of-round more than .001" or tapered, the shaft should be replaced or reconditioned. Check the crankshaft thrust faces at the rear main bearing for scoring or excessive wear.
13. Inspect the connecting rod bearings for damage that would make replacement necessary.
14. Determine whether or not pistons are to be replaced. New piston assemblies and rings are required when the cylinders are to be honed or rebored. If the pistons are to be used again, check the piston pin fit.
15. Inspect the timing chain sprockets for excessive tooth wear. Inspect the chain for signs of wear.
16. Check the cylinder heads for being warped, for having clogged water passages, cracked valve seats or worn valve bores.
17. Inspect the manifolds for excessive carbon in the ports. Clean the carbon deposits from the intake manifold oil splash guard under the exhaust cross-over passage. Check the operation of the heat control valve.
18. Inspect the oil pump gears for wear, check the shaft for looseness in the housing and the inside of cover for wear that would permit oil to leak past end of gears.
19. Instructions for inspection and repair of the fuel pump, carburetor, air cleaner, generator, starting motor, distributor, clutch and water pump will be found in their respective sections of this manual.

The performance of the following operations is contingent upon engine condition at time of overhaul as determined in the inspection.

If the cylinder block inspection indicated that the block was suitable for continued use except for out-of-round or tapered cylinders, they can be conditioned by honing or boring and honing.

High limit standard size pistons are available for service use so that proper clearances can be obtained for slightly worn cylinder bores requiring only light honing to clean up the bores. There are four standard size pistons available for service installation. In addition, aluminum pistons are serviced in .020", .030" and .040" oversizes. If the cylinders were found to have less than .005" taper or wear they can be conditioned with a hone and fitted with the high limit standard size pistons. A cylinder bore of less than .005" wear or taper may not entirely clean up when fitted to a high limit piston. If it is desired to entirely clean up the bore in these cases, it will be necessary to rebore for an oversize piston. If more than .005" taper or wear, they should be bored and honed to the smallest oversize that will permit complete resurfacing of all cylinders.

Cylinder Boring

1. Before using any type boring bar, the top of the cylinder block should be filed off to remove any dirt or burrs. This is very important. Otherwise, the boring bar may be tilted which would result in the rebored cylinder wall not being at right angles to the crankshaft.
2. In Chevrolet engines, the piston clearance is provided for on the piston and this must be taken into consideration when setting the cutter in the boring bar. The piston to be fitted should be checked with a micrometer, measuring just below the lower ring groove and at right angles to the piston pin. The cylinder should be bored to the same diameter as the piston.
3. If a micrometer is not available to measure the piston, the cylinder should be bored .002" less than the oversize piston to be fitted.
4. The instructions furnished by the manufacturer of the equipment being used should be carefully followed.

Cylinder Honing and Piston Fitting

1. When the cylinders are to be honed only for use of standard high limit piston or for final finishing after they have been rebored to within .002" of the desired size, they should be finish honed and polished with a hone. Rough stones may be used at first and fine stones for the polishing operation.
2. Follow the hone manufacturers recommendations for the procedure on the use of the hone and cleaning and lubrication during honing.
3. Occasionally during the honing operation, the cylinder bore should be thoroughly cleaned and the piston selected for the individual cylinder checked for correct fit.
4. Check fit of the aluminum pistons in the following manner:
   • Invert the piston, skirt end up, and place a .0015" by 1/2" wide feeler ribbon, part of Piston Fitting Gauge and Scale, J-5513 on the side of the piston 90° from the piston pin holes.
   • Insert the feeler ribbon and inverted piston into the cylinder bore so that the center of the piston pin is flush with the top surface of the cylinder block. Keep the feeler ribbon straight up and down and keep the piston pin parallel with the crankshaft axis.
   • Pull the feeler gauge straight up and out, noting at the same time the scale reading, which should be between 7 and 18 pounds (fig. 98).
   • If the scale reading is greater than the maximum allowable pull, try another piston or lightly hone the cylinder bore to obtain the proper fit.
   • Should the scale reading be less than the minimum allowable pull, try another piston, or if standard size, try a standard high limit piston. If proper fit cannot be obtained it will be necessary to rebore the cylinder to the next oversize piston.
   • Mark each piston after fitting to correspond with the cylinder to which it has been fitted. This will assure proper installation.
5. Permanently mark the piston for the cylinder to which it has been fitted and proceed to hone cylinders and fit the remaining pistons. CAUTION: Handle the pistons with care and do not attempt to force them through the cylinder until the cylinder has been bored to correct size as this type piston can be distorted through careless handling.
6. Thoroughly clean the cylinder bores. It is extremely essential that a good cleaning operation be performed. If any of the abrasive material is allowed to remain in the cylinder bores, it will rapidly wear the new rings and cylinder bores in addition to the bearings lubricated by the contaminated oil. The bores should be swabbed several times with light engine oil and a clean cloth and then wiped with a clean dry cloth. Cylinder should not be cleaned with kerosene or gasoline. Clean the remainder of the cylinder block to remove the excess material spread during the honing operation.

Crankshaft main bearing service may be performed with the engine inverted and oil pan, spark plugs, oil pump and timing chain removed. The Plastigage method of measuring bearing clearance is recommended on both main and connecting rod bearings.

Bearing and Journal Inspection

Whenever the bearings are adjusted, the bearing insert and the journal should be inspected. In general, the lower half of the bearing shows a greater wear and the most distress from fatigue. If upon inspection the lower half is suitable for use, it can safely be assumed that the upper half is also satisfactory. If the lower half shows evidence of fatigue, distress, abrasion, erosion, scoring or the like, both upper and lower halves should be replaced. Never should one-half be replaced without replacing the other half.

If the running clearance of a bearing is too great with the used inserts, it will be necessary to install both upper and lower bearing halves. Should this become necessary, the crankshaft journal should be checked with a micrometer for out-of-round, taper or underside. Experience has shown that clearance increase from wear in main bearings is not only due to bearing wear, but is also due in part to crankshaft journal wear.

Main Bearing Adjustment

Plastigage consists of a wax-like plastic material which will compress evenly between the bearing and journal surfaces without damaging either surface. To obtain the most accurate results with Plastigage, certain precautions should be observed. If the engine is out of the chassis and upside down, the crankshaft will rest on the upper bearings and it can be assumed that the total clearance can be measured between the cap bearing and journal.

NOTE: To assure the proper seating of the crankshaft, the rear main bearing oil seal should be removed and all bearing cap bolts should be at their specified torque. In addition, preparatory to checking fit of bearings, the surface of the crankshaft journal and bearing should be wiped clean of oil.

1. Starting with the rear main bearing, remove bearing cap and wipe oil from journal and bearing cap.
2. Place a piece of Plastigage the full width of the bearing (parallel to the crankshaft) on the journal (fig. 99).
3. Install the bearing cap and evenly tighten the retaining bolts to 60-70 lb. ft. torque. CAUTION: Do not rotate the crankshaft while the Plastigage is between the bearing and journal.
4. Remove bearing cap. The flattened Plastigage will be found adhering to either the bearing shell or journal. On the edge of Plastigage packing envelope there is a graduated scale which is correlated in thousandths of an inch.
5. Without removing the Plastigage, check its compressed width (at the widest point) with the graduations on the Plastigage envelope (fig. 100). NOTE: Normally, main bearing journals wear evenly and are not out-of-round. However, if a bearing is being fitted to an out-of-round journal be sure to fit to the maximum diameter of the journal. If the bearing is fitted to the minimum diameter of the journal and the journal is out-of-round .001" or more, interference between the bearing and journal will result in rapid bearing failure. If the flattened Plastigage tapers toward the middle or ends, there is a difference in clearance indicating a taper, low spot or other irregularity of the bearing or journal. Be sure to check the journal with a micrometer if the flattened Plastigage indicates more than .001" difference.
6. If the bearing clearance is not over .004" (worn), or, .003" (new) or less than .001" the bearing insert is satisfactory. If the clearance is not within these limits replace the insert.
7. A .002" undersize bearing may produce the proper clearance. If not, it will be necessary to regrind the crankshaft journal for use with the next undersize bearing. NOTE: Bearings are available in standard sizes and .002", .010", .020" and .030" undersize.
8. Proceed to next bearing. After all bearings have been checked rotate the crankshaft to see that there is no excessive drag.
9. Check the end play by forcing the crankshaft to its extreme front position. Check at the front end of the rear main bearing with a feeler gauge (fig. 101). This clearance should be from .002" to .006".
10. Install a new rear main bearing oil seal in the cylinder block and main bearing cap. Insert the seal in the groove by hand, place Rear Main Bearing Oil Seal Replacer J-5788 on the seal and, using a hammer on the end of the tool, seat the seal in the groove (fig. 102). With the tool in place, cut the protruding ends of the seal with a sharp knife flush with the cylinder block or bearing cap.

Main Bearings-Replace

The main bearings used as service replacement are of high quality with close tolerances of fit and will not require line reaming on installations. The close dimensional tolerances assure an equalized bearing surface at all points on the crankshaft when replaced in sets.

1. Remove main bearing caps and connecting rod caps and lift crankshaft out of cylinder block. Push pistons to top of bores.
2. Inspect the crankshaft. All main bearings are ground to 2.2978"-2.2988", and crankpin journals to 1.999"-2.000".
   These dimensions should be checked with a micrometer for out-of-round, taper or undersize. If the journals exceed .001" out-of-round or taper the crankshaft should be replaced or reconditioned to an undersize figure that will enable the installation of underside precision type bearings.
   The crankshaft should also be checked for runout. To perform this operation, support the crankshaft at the front and rear main bearing journals in "V" blocks and indicate the runout of both the rear intermediate and front intermediate journals, using a dial indicator. The runout limit of each of these journals is .002". If the runout exceeds .002" the crankshaft must be straightened.
3. Remove old bearing shells from cylinder block and caps.
4. Remove rear main bearing oil seal.
5. Install new bearing shells in the cylinder block and caps. NOTE: Main bearing shells with oil holes are the upper halves of holes bearing shells and are inserted between the crankshaft and cylinder block.
6. Carefully place the crankshaft in the bearings.
7. Install the bearing caps. Tighten bolts to 60 to 70 ft. lbs. torque. NOTE: The caps are marked with an arrow for identification purposes. The caps are to be installed with the arrows pointing to the front of the engine.
8. Check crankshaft end clearance at the rear main bearing. It should be .002" to .006".
9. Adjust main bearings as previously outlined.
10. Install new rear bearing oil seal as outlined under Oil Seal Rear Bearing-Replace.
11. Install connecting rod bearings and caps.

Piston and connecting rod operations may be performed with the engine either in or out of the vehicle. Procedure remains the same in either case.

Removal of Piston and Connecting Rod Assemblies

1. Remove oil pan and oil pump.
2. Remove cylinder heads.
3. Remove ridge in top of cylinder bores with a ridge reamer. CAUTION: Do not over-cut ridge. Remove ridge only Rush with bore at top of piston travel.
4. Remove connecting rod journal bearing caps and install J-5239-1 and 2 Connecting Rod Guide Set on studs. Push piston assemblies out of top of cylinder block.

Connecting Rod Alignment

When connecting rod and piston assemblies are removed from an engine the wear pattern on the piston skirts should be symmetrical on each side. Bent or misaligned connecting rods will cause an off angle wear pattern. When this condition exists, the piston, pin, and rod assembly should be replaced.

1. A check of a piston and connecting rod assembly for both cock and twist can be made without disassembling the rod from the piston. Mount the connecting rod and piston assembly on the alignment fixture and set the piston in line with the connecting rod. Then place the "V" block on the piston skirt. If both pins on the block contact the face plate, the rod is not cocked (fig. 103).
2. Then, with the "V" block on the piston skirt and the pins against the face plate, tip the piston first in one direction and then in the other. If the pins on the block remain against the face plate, there is no twist in the connecting rod.
3. If one pin leaves the face plate while the piston is being tipped in one direction and the other pin leaves the face plate while the piston is being tipped in the other direction, the connecting rod is twisted and should be straightened until both pins follow the face plate.

Disassembly

1. Install pilot of Piston Pin Removing and Installing Tool, No. J-5538 on puller screw.
2. Install puller screw, with pilot, through piston and pin.
3. Install support over threaded end of puller screw with small end of support against piston.
4. Install nut loosely on puller screw and place assembly in an arbor press as shown in Fig. 104. Press pin out of connecting rod.
5. Remove assembly from press and remove puller nut, support and piston pin from puller screw.
6. Remove puller screw from piston and remove pilot from piston and connecting rod.
7. Remove connecting rod from piston.

Checking Piston Pin Fit

Piston pins should be capable of supporting their own weight in either pin boss (fig. 105) when coated with fight engine oil and at 60°F. Higher or lower temperatures will cause false indications. Pistons and pins are serviced as assemblies.

Assembly

1. Lubricate piston pin holes in piston and connecting rod to facilitate installation of pin.
2. Position connecting rod in its respective piston so that flange or heavy side of rod at the bearing end will be towards front of piston (cast depression in top of piston head and cast "F" marks on piston struts) on 1, 3, 5 and 7 pistons, and the rod flange to the rear of the piston on 2, 4, 6 and 8 pistons.
3. Install piston pin on puller screw and pilot on puller screw (fig. 106).
4. Install puller screw through piston and rod, indexing pilot through piston and rod.
5. Install support over threaded end of puller screw with smaller diameter toward piston.
6. Install nut on puller screw and tighten with torque wrench to start piston pin into connecting rod (fig. 107). CAUTION: If pin can be started into connecting rod with less than 15 ft. lbs. minimum torque, the clearance between piston pin and rod is excessive and either the piston and pin assembly or connecting rod must be replaced.
7. Install in arbor press and press piston pin in until pilot bottoms in support, properly positioning the pin in the rod.

Piston pins are a matched fit to the piston and are not available separately. Piston pins will not become loose enough to cause a knock or tapping until after very high mileages and in such cases a new piston and pin assembly should be installed.

Piston Rings

Flex type oil control rings are now used in all Chevrolet engines. Previously the oil control ring was a four piece ring with an expander placed behind the separator. The new flex type oil control ring consists of two rails and a flexible segmented spacer that serves as a combination spacer and expander on the rails. Constant pressure is maintained on cylinder walls by the rails which are held firm but not rigidly by the flexible spacer; severe ring pressure is averted to increase ring and cylinder wall wear.

This type compression ring takes its name, twist type, from its installed position which is cocked or twisted. It assumes and maintains this position for life because the upper edge of its diameter is chamfered, making the ring unbalanced in cross section.

All compression rings are marked with the word "TOP" cast in the upper side of the ring. When installing compression rings, make sure the side marked "TOP" is toward the top of the piston. The top ring is chrome flashed for maximum life.

The oil control rings used are of the four piece type, using a crimped flat spring steel expander behind two steel rails and a separator. Chevrolet piston rings are furnished in standard sizes as well as .020", .030" and .040" oversizes.

Compression Ring Installation

1. Select rings comparable in size to the pistons being used.
2. Slip the ring in the cylinder bore; then using the head of a piston, press the ring down into the cylinder bore about two inches. NOTE: Using a piston in this way will place the ring square with the cylinder walls.
3. Check the space or gap between the ends of the ring with a feeler gauge (fig. 108). This gap should be from .007" to .020".
4. If the gap between the ends of the ring is less than .007", remove the ring and try another for fit, or the gap in the tight fitting ring may be enlarged as follows.
5. Remove the ring from the cylinder. Clamp a fine cut file in a vise and, grasping each end of the ring firmly between the thumb and fingers, work the two ends of the ring across the surfaces of the file. Press the ring together at the gap lightly until the proper gap is obtained. Be careful not to distort the ring during this operation or it may bind in the ring groove of the piston. Fit each ring separately to the cylinder in which it is going to be used.
6. New pistons, rings and cylinder bores wear considerably during seating and gaps widen quickly; however, engine operation will not become seriously affected if ring gaps do not become greater than 1/32".
7. Carefully remove all particles of carbon from the ring grooves in the piston and inspect the grooves carefully for burrs or nicks that might cause the rings to hang up.
8. Slip the outer surface of the ring into the piston ring groove and roll the ring entirely around the groove to make sure that the ring is free and does not bind in the groove at any point (fig. 109). If binding occurs, the cause should be determined and removed by carefully dressing with a fine cut file. However, if the binding is caused by a distorted ring, install a new ring.
9. Proper clearance of the piston ring in its piston ring groove is very important in maintaining engine performance and in preventing excessive oil consumption. Therefore, when fitting new rings, the clearances between the top and bottom surfaces of the ring grooves should be inspected.
10. The compression rings should be fitted so that the clearance is .001" to .003" (fig. 110).
11. Assemble the rings to the pistons as they are fitted and make a final test of the ring fit in the grooves by repeating the fitting procedure given above.

Oil Control Ring Installation

1. Install the oil ring spacer in the oil ring groove and position gap in line with piston pin hole. Hold spacer ends butted and install steel rail on top side of spacer. Position gap at least 1" to left of spacer gap, then install second rail on lower side of spacer. Position gap at least 1" to right of spacer gap.
2. Flex the oil ring assembly in its groove to make sure ring is free and does not bind in the groove at any point. If binding occurs, the cause should be determined and removed by carefully dressing with a fine cut file. However, if the binding is caused by a distorted ring, install a new ring.
3. Proper clearance of the piston ring in its piston ring groove is very important in maintaining engine performance and in preventing excessive oil consumption. Therefore, when fitting new rings, check the clearances between the top and bottom surfaces of the ring grooves. Refer to "Engine Specifications" for correct clearances.

Piston and Connecting Rod Assembly Installation

1. Lightly coat pistons, rings and cylinder walls with light engine oil.
2. With bearing caps removed, install Connecting Rod Guide Set J-5239 on bearing cap bolts.
3. Install each piston in its respective bore, using Guide set on each assembly. The side of the piston with the cast depression in the head and the cast "F" marks should be to the front of the cylinder block. Use either Piston Ring Compressor J-5601 or KMO 357 (fig. 111) to compress the rings for installation. Guide the connecting rod bearing into place on the crankshaft journals with the long detail of J-5239 Connecting Rod Guide Set.
4. Install the bearing caps and adjust the bearings as described under "Connecting Rod Bearings-Adjust."

ADJUSTMENT

Connecting rod bearing inserts are available in standard sizes and undersides of .001", .002", .010" and .020". These bearings are not shimmed and when clearances become excessive the next underside bearing insert should be used. DO NOT FILE ROD OR ROD CAPS.

1. Remove the connecting rod bearing cap.
2. Wipe bearing insert shell and crankpin clean of oil.
3. Place a piece of Plastigage the full width of the bearing or crankpin (parallel to the crankshaft) . ( fig. 112).
4. Reinstall the bearing cap and evenly tighten the retaining bolts to 30-35 ft. lbs. torque. CAUTION: Do not turn crankshaft with the Plastigage installed.
5. Remove the bearing cap and without removing the Plastigage, check its width at the widest point with the Plastigage scale (fig. 113). NOTE: If the crankpin is out-of-round be sure to fit the bearing to the maximum diameter of the crankpin. If the flattened plastic is not uniform from end to end in its width, the crankpin or bearing is tapered, has a low spot or some other irregularity. Check the crankpin with a micrometer for taper if the flattened Plastigage indicates more than a .001 " difference.
6. If the reading is not over .004" (worn), or .003" (new) or not less than .001" the fit is satisfactory. If however, the clearances are not within these limits, replace the bearing with the proper underside bearing. NOTE: The insert bearing shells are not adjustable and no attempt should be made to adjust by filing the bearing caps.
7. Rotate the crankshaft after bearing adjustment to be sure the bearings are not too tight.
8. Check connecting rod clearance between upper half of connecting rod and side of crank pin. This clearance should be .008" to .014" with two rods on each throw of crankshaft (fig. 114).

1. Pry old seal out of cover from the front with a large screwdriver.
2. Install new seal so that open end of the seal is toward the inside of the cover and drive it into position with oil seal driver J-995 (fig. 84). CAUTION: Support seal portion of cover while installing seal.

CYLINDER HEADS AND VALVES

Recondition and assemble the cylinder heads and valves as outlined under Care, Maintenance and Adjustments.

OIL PUMP ASSEMBLY

1. Place drive gear and shaft in pump body.
2. Install idler gear so that smooth side of gear will be toward the cover.
3. Install cover and attaching screws. Tighten screws to 6 to 9 ft. lbs. and check to see that shaft turns freely.
4. Install pick-up screen on pipe and bend float travel control tang back in place.
5. Assemble collar end of extension shaft assembly over pump drive shaft, aligning tang of extension shaft with slot in end of pump drive shaft. Install retaining clip with flat end of clip in groove of pump drive shaft.

Installation, and Alignment Check

1. Install clutch housing (standard shift models) or flywheel housing (Powerglide Models) to cylinder block over dowel pins, install attaching bolts and tighten to 25 to 35 ft. lbs.
2. Install J-2494 Indicator Post in one of the crankshaft flange bolt holes. On Powerglide models, install J-4656-A indicator swivel on indicator post.
3. Install KMO 30 Dial Indicator and position to read bore runout of the housing (fig. 115). Check runout by rotating crankshaft. On standard shift models, the limit is .008", while Powerglide models have a limit of .005".
4. On Powerglide models only, reposition the dial indicator to read face runout and rotate crankshaft. On Powerglide models, .007" is the maximum allowable runout (fig. 116).
5. Remove indicator and attachments.

Alignment Correction

NOTE: When applying this alignment correction to clutch housing of the three speed transmission models, face parallelism should be disregarded as this alignment check must be made with the transmission case assembled to housing. This alignment correction is covered in the transmission section.

1. If bore runout is in excess of .005" or if housing face parallelism exceeds .007", remove indicator and the housing from engine block.
2. Remove the cylinder block to housing dowel pins.
3. Clean mating faces of housing and engine block and make certain there are no burrs or metal extrusion around dowel or bolt holes.
4. Install flywheel housing and tighten attaching bolts evenly to 25-35 ft. lbs. torque.
5. Mount indicator on indicator post and indicate flywheel housing face. Set indicator at zero at the six o'clock position and carefully check indicator readings at the 9, 12 and 3 o'clock positions. The runout limit is .007". NOTE: Care should be exercised so that the indicator button is not on the edge of a bolt hole when the readings are taken.
6. If the face runout exceeds .007", shim as necessary, using a main bearing shim between the housing and block at the attaching bolt locations.
7. After the housing face has been brought within the .007" limit with bolts tightened to 25-35 ft. lb. torque, reset indicator to read zero at the six o'clock position on the machined inside diameter of the flywheel housing bore. NOTE: Be careful that the indicator button is centered on the narrow machined flange and does not touch flange step.
8. Check indicator readings at the 9, 12 and 3 o'clock positions, carefully lifting indicator button over each cutaway section of flange on Powerglide models (fig. 117). The runout should not exceed .005".
9. If the readings exceed the .005" runout limits, loosen bolts slightly and tap housing with a soft hammer in required direction until runout is within limits. Tighten attaching bolts evenly to 25-35 ft. lb. torque and recheck.
10. With housing in proper alignment, carefully ream holes, using a 21/32" reamer.
11. Blow out holes and then install special oversize dowels.
12. Recheck flywheel housing bore and the face to make sure they still are within proper limits.
13. Remove indicator and attachments.

1. Clean the mating flanges of flywheel and crankshaft carefully and make sure there are no burrs on either mounting face.
2. Place the flywheel in the clutch housing and position it so that the dowel in crankshaft flange will enter the hole in the flywheel.
3. Install the six bolts and lock washers.
4. Tighten bolts to 55-65 foot pounds with a torque wrench.
5. On all models except Powerglide models, mount a dial indicator on the clutch housing so that the button of the indicator will contact the machined surface of flywheel (fig. 118), and check the flywheel runout.
6. Runout should not exceed .008". If excessive, remove flywheel and recheck for burrs or replace flywheel.

The following engine assembly is to be performed after the crankshaft, connecting rods and pistons, clutch or flywheel housing and flywheel have been installed as previously outlined.

1. Install six new oil gallery plugs in front and rear of cylinder block.
2. Assemble oil pump and extension shaft assembly to rear main bearing cap, aligning slot on top end of extension shaft with drive tang on lower end of distributor drive shaft.
3. Install oil pump to rear main bearing cap bolt and tighten to 45 to 50 ft. lbs.
4. Install two 5/16 -18 x 4" bolts in camshaft, lubricate camshaft and install camshaft in engine. Remove bolts.
5. Install crankshaft timing sprocket on crankshaft, aligning keyway with key installed in crankshaft. Drive in place, using a hammer and J-5590, Transmission Front Bearing Installer (fig. 119).
6. Rotate crankshaft until "0" mark on crankshaft sprocket is up toward camshaft.
7. Install timing chain on camshaft sprocket. Hold the sprocket vertical with the chain hanging below, and orient to align "0" marks on camshaft and crankshaft sprockets.
8. Align dowel in camshaft with dowel hole in camshaft sprocket and install sprocket on camshaft.
9. Draw camshaft sprocket onto camshaft, using the three mounting bolts. Do not drive sprocket, as camshaft bore rear plug can be driven out of block. Tighten to 15-20 ft. lbs. torque.
10. Lubricate timing chain with engine oil.
11. Install crankshaft oil slinger on crankshaft.
12. Make certain that cover mounting face and cylinder block front end plate face are clean.
13. Coat the oil seal with light grease and, using a new cover gasket, install cover and gasket over dowel pins in cylinder block.
14. Install cover screws and tighten to 6-7 1/2 ft. lb. torque.
15. Install two 3/18 - 16 x 1 1/2" capscrews in harmonic balancer. Position harmonic balancer on crankshaft, aligning the key on the crankshaft with the key way in the balancer.
16. Using Transmission Front Bearing Installer J-5590, drive balancer on crankshaft until the hub bottoms on the crankshaft timing sprocket.
17. Remove two cap screws from balancer.
18. Thoroughly clean all oil pan gasket sealing surfaces.
19. Install rear oil pan seal in groove in rear main bearing cap. Tuck ends into groove openings in cylinder block.
20. Install side gaskets on pan rails, using grease as a retainer. Rear ends lap end gasket. Tuck front ends of side gaskets into gap between front end cover seal groove and cylinder block.
21. Install oil pan front seal in groove in front end cover, with ends butting side gaskets.
22. Install oil pan to cylinder block bolts. Tighten front and rear 5/16" 'bolts to 12 to 15 ft. lbs., intermediate 1/4" bolts should be tightened to 6-9 ft. lbs.
23. Install oil pan drain plug.
24. Install inner crankcase ventilator body to crankcase and install retaining screw. Use caution to avoid damage to vent body.
25. Install the valve lifters in same bores as removed.
26. Thoroughly clean out cylinder head bolt holes in the block and clean cylinder bolt threads. Then place new cylinder head gaskets in position on cylinder block. Use a good head gasket. paste with these steel gaskets.
27. Place the cylinder heads in position over the two dowel pins in the block.
28. Oil the threads of all long cylinder head bolts. Coat threads of all short cylinder head bolts with special sealing compound, such as Permatex No. 3. These bolts protrude into the water passages and require this compound to prevent rusting.
29. Install bolts finger tight.
30. Tighten the cylinder head bolts a little at a time in the order shown (fig. 80). The final tightening should be 60-70 ft. lbs.
31. Install 16 push rods in their respective bores.
32. Insert pivots in valve rocker arms, rocker arms over studs, and install nuts.
33. Clean gasket faces of intake manifold and cylinder heads.
34. Install intake manifold end gaskets on cylinder block. Coat ends of intake manifold side gaskets around water passages with a good gasket sealing compound and install on cylinder heads.
35. Install intake manifold and bolts with pipe clips and plug wire supports in place. Tighten finger tight. Tighten bolts a little at a time according to the sequence shown in fig. 81. Final torque should be 25-35 ft. lbs.
36. Clean all spark plugs with abrasive type cleaner, inspect for damage and set gap at .035" using a round feeler gauge.
37. Place new gaskets on plugs and install. Tighten to 20-25 ft. lbs.
38. Install plug wiring harness. CAUTION: Plug wire location is extremely important. Numbers formed in rubber support grommets show sequence.
39. Install thermostat, water outlet gasket and thermostat housing and tighten bolts to 18 to 23 ft. lbs. Install water pump. Tighten bolts to 25 to 35 ft. lbs.
40. Install carburetor. On Powerglide models, install transmission throttle control upper rod to carburetor.
41. Install push rod, fuel pump mounting plate gasket, mounting plate, fuel pump gasket and fuel pump. Mounting plate bolts should be tightened to 6 to 9 ft. lbs. Install fuel pump to carburetor feed pipe.
42. Install eye bolts from Lift Kit J-4536-A in appropriate cylinder head bolt holes. Engine may have to be removed from stand for following steps, depending on stand used.
43. Coat end of exhaust manifold gaskets around water passages and exhaust manifold bolts with a graphite type grease. Install exhaust manifolds and bolts. Tighten to 25-35 ft. lbs. torque.
44. Clean mating surfaces and install exhaust manifold heat control valve and exhaust cross-over pipe, using new gaskets and seals.
45. Install generator on left bank exhaust manifold.
46. On all standard shift models:
    • Lubricate the clutch pilot bearing with a small amount of high melting point grease. Place the clutch disc and clutch cover assembly in position and install the Pilot Tool J-5824.
    • Turn the clutch cover until the "X" on the cover lines up with the "X" on the flywheel ( fig. 93). Install the attaching bolts loosely and then tighten them a turn at a time to take up the spring pressure evenly and prevent clutch distortion. Tighten bolts to 25-30 foot pounds torque with a torque wrench and then remove pilot tool.
    • Pack the clutch fork ball seat with a small amount of high melting point grease and snap the fork onto the ball with the end extending through opening in clutch housing.
    • Install clutch throw-out bearing.
    • Install transmission and tighten attaching bolts securely.
    • Install flywheel underpan and extension.
47. On models equipped with Powerglide transmissions:
    • Remove Converter Assembly Holding Tool J-5384. Install transmission on flywheel housing and tighten attaching bolts securely.
    • Install converter to flywheel bolts and tighten to 25 to 30 ft. lbs..
    • Install flywheel housing cover and starting motor.
    • Install crankcase breather road draft tube.

1. Install exhaust manifold heat control valve and gaskets and install exhaust cross-over pipe and packing.
2. Tilt and lower engine and transmission assembly into the chassis as a unit, guiding engine to align supports with frame.
3. Install rear mounts and bolts and snug-up bolts.
4. Install front mounts, and tighten nuts against spacers.
5. Remove lifting attachments, install cylinder head bolts and tighten to 60-70 ft. lb. Tighten rear mount bolts.
6. Install rocker arm cover gaskets, covers and screws with reinforcements.
7. Install automatic choke heat tube.
8. Slide propeller shaft front universal joint on transmission output shaft, raise rear of propeller shaft, index rear universal joint yoke with pinion shaft companion flange and install U-bolts and nuts. Tighten securely.
9. On conventional transmission models: Install clutch bell crank, connect clutch pedal adjusting link to clutch fork and adjust to give 3/4" to 1" free pedal travel.
10. On all models having a 3-speed transmission:
    • Connect speedometer cable to speedometer driven gear.
    • Connect transmission control rods to shifter levers on transmission side cover. Adjust control rods as outlined in "Transmission Section."
    • Check transmission lubricant level.
    • If equipped with overdrive, connect associated wires and cables.
11. On all models having a Powerglide transmission:
    • Connect speedometer cable to speedometer driven gear.
    • Connect transmission control rod to transmission control rod bell crank and adjust rod as outlined in "Transmission Section."
    • Install transmission filler tube and dip stick.
    • Install transmission throttle control rod.
12. Replace exhaust pipe to cross-over pipe and tighten attaching bolts securely.
13. Connect vacuum lines.
14. Connect wire to oil pressure gauge and install temperature element in cylinder head.
15. Install air cleaner. NOTE: If oil bath cleaner is used, disassemble, clean and refill before installing.
16. Attach generator and field wires to generator.
17. Attach gasoline line to fuel pump.
18. Mount coil and install distributor. (See Engine-Electrical for installation procedure.)
19. Attach coil wires to distributor.
20. Install battery box and battery. Attach battery cable and ammeter wire to large terminal on solenoid and starter switch wire to small terminal and connect coil wire to coil.
21. Install fan pulley and fan blade. Install radiator core and spacer shims as required.
22. Install oil cooler lines on all Powerglide models, and connect radiator hoses.
23. Refill radiator and crankcase.
24. Install wiper motor.
25. Install and adjust fan belt to 13/16" deflection.
26. On all models with standard transmission, start engine and allow to run until properly normalized and adjust valves as outlined under "Valve Adjustment."
27. On all models with the Powerglide transmission, use oil filler tube and funnel J-4264 and fill transmission as follows:
    • Fill transmission with five quarts of Automatic Transmission Fluid, "Type A."
    • Start engine and let idle with transmission selector lever in "N" position. Check oil level and if necessary add oil to bring fluid level to "Full" mark on the dip stick. Do not overfill.
28. On Powerglide equipped cars, place selector lever in reverse and check linkage adjustment as outlined in the "Transmission Section."
29. Replace hood assembly, aligning previously scribed marks.

ENGINES

Symptom and Probable Cause
Probable Remedy

LACK OF POWER

1. Poor Compression

a. Incorrect valve lash
a. Adjust valve lash according to instructions under "Valve Adjustment"

b. Leaky valves
b. Remove cylinder head and grind valves

c. Valve stems or lifters sticking
c. Free up or replace

d. Valve springs weak or broken
d. Replace springs

e. Valve tiring incorrect
e. Correct valve timing

f. Leaking cylinder head gasket
f. Replace gasket

g. Piston rings broken
g. Replace rings

h. Poor fits between pistons, rings and cylinders
h. Overhaul engine

2. Ignition System Improperly Adjusted

a. Ignition not properly timed
a. Set ignition according to instructions under "Engine Tune-Up"

b. Spark plugs faulty
b. Replace or clean, adjust and test spark plugs

c. Distributor points not set correctly
c. Set distributor points and time engine

3. Lack of Fuel

a. Dirt or water in carburetor
a. Clean carburetor and fuel pump

b. Gas lines partly plugged
b. Clean gas lines

c. Clean gas tank
c. Dirt in gas tank

d. Air leaks in gas line
d. Tighten and check gas lines

e. Fuel pump not functioning properly
e. Replace or repair fuel pump

4. Carburetor Air Inlet Restricted

a. Air cleaner dirty
a. Clean air cleaner

b. Carburetor choke partly closed
b. Adjust or replace choke mechanism

5. Overheating

a. Lack of water
a. Refill system

b. Fan belt loose
b.Adjust or replace

c. Fan belt worn or oil soaked
c. Replace belt

d. Thermostat sticking closed
d. Replace thermostat

e. Water pump inoperative
e. Replace water pump

f. Cooling system clogged
f. Clean and reverse flush

g. Incorrect ignition or valve timing
g. Retime engine

h. Brakes dragging
h. Adjust brakes

i. Improper grade and viscosity oil being used
i. Change to correct oil

j. Fuel mixture too lean
j. Overhaul or adjust carburetor

k. Valves improperly adjusted
k. Adjust valves

l. Defective ignition system
l. See "Engine Tune-Up"

m. Exhaust system partly restricted
m. Clean or replace

6. Overcooling

a. Thermostat holding open
a. Replace thermostat

EXCESSIVE OIL CONSUMPTION

1. Leaking Oil

a. Oil pan drain plug loose
a. Tighten drain plug

b. Oil pan retainer bolts loose
b. Tighten oil pan bolts

c. Oil pan gaskets damaged
c. Replace pan gaskets

d. Timing gear cover loose or gasket damaged
d. Tighten cover bolts or replace gasket

e. Oil return from timing gear case to block restricted, causing leak at crankshaft fan pulley hub on six cylinder models
e. Remove oil pan and clean oil return passages

f. Rocker arm cover gaskets or, on six cylinder models, push rod cover damaged or loose
f. Tighten covers or replace gaskets

g. Fuel pump loose or gasket damaged
g. Tighten fuel pump or replace gasket

h. Rear main bearing leaking oil into clutch housing or flywheel housing
h. Adjust or replace main bearing or main bearing oil seal.

2. Burning Oil

a. Broken piston rings
a. Replace rings

b. Rings not correctly seated to cylinder walls
b. Give sufficient time for rings to seat. Replace if necessary

c. Piston rings worn excessively or stuck in ring grooves
c. Replace rings

d. Piston ring oil return holes clogged with carbon
d. Replace rings

e. Excessive clearance between piston and cylinder wall due to wear or improper fitting
e. Fit new pistons

f. Cylinder walls scored, tapered or out-of-round
f. Recondition cylinders and fit new pistons

HARD STARTING

1. Slow Cranking

a. Heavy engine oil
a. Change to lighter oil

b. Partially discharged battery
b. Charge battery

c. Faulty or undercapacity battery
c. Replace battery

d. Poor battery connections
d. clean and tighten or replace connections

e. Faulty starter switch
e. Replace switch

f. Faulty starting motor or drive
f. Overhaul starting motor

2. Ignition Trouble

a. Distributor points burned or corroded
a. Clean or replace points

b. Points improperly adjusted
b. Readjust points to .016", adjust new points to .019"

c. Spark plugs improperly gapped
c. Set plug gap at .035"

d. Spark plug wires loose and corroded
d. Clean wire and cap terminals in distributor cap

e. Loose connections in primary circuit
e. Tighten all connections in primary circuit

f. Series resistance in condenser circuit
f. Clean all connections in condenser circuit

g. Low capacity condenser
g. Install proper condenser

h. Ballast resister faulty or out of circuit
h. Inspect and correct

3. Engine Condition

a. Valves holding open
a. Adjust valves

b. Valves burned
b. Grind valves

c. Leaking manifold gasket
c. Tighten manifold bolts or replace gasket

d. Loose carburetor mounting
d. Tighten carburetor

e. Faulty pistons, rings or cylinders
e. See "Poor Compression"

4. Carburetion

a. Choke not operating properly
a. Adjust or repair choke mechanism

b. Throttle not set properly
b. Set throttle

c. Carburetor dirty and passages restricted
c. Overhaul carburetor

POPPING, SPITTING AND DETONATION

1. Overheated Intake Manifold

a. Manifold heat control spring not properly installed
a. Adjust according to instructions under "Engine Tune-Up"

b. Manifold heat control valve sticking
b. Free up heat control valve

2. Ignition Trouble

a. Loose wiring connections
a. Tighten all wire connections

b. Faulty wiring
b. Replace faulty wiring

c. Faulty spark plugs
c. Clean or replace and adjust plugs

3. Carburetion

a. Lean combustion mixture
a. Clean and adjust carburetor

b. Dirt in carburetor
b. clean carburetor

c. Restricted gas supply to carburetor
c. Clean gas lines and check for restrictions

d. Leaking carburetor or intake manifold gaskets
d. Tighten carburetor to manifold and manifold to head bolts or replace gaskets

4. Valves

a. Valves adjusted too tight
a. Adjust valve lash

b. Valves sticking
b. Lubricate and free up. Grind valves if necessary

c. Exhaust valves thin and heads overheating
c. Replace valves

d. Weak valve springs
d. Replace valve springs

e. Valves timed early
e. Retime

5. Cylinder Head

a. Excessive carbon deposits in combustion chamber
a. Remove head and clean carbon

b. Cylinder head water passages partly clogged
b. Remove cylinder head and clean water passages causing hot spot in combustion chamber

c. Partly restricted exhaust ports in cylinder head
c. Remove cylinder head and clean exhaust ports

d. Cylinder head gasket blown between cylinders
d. Replace cylinder head gasket

6. Spark Plugs

a. Spark plugs glazed
a. Clean or replace spark plugs

b. Wrong heat range plug being used
b. Change to correct spark plugs

7. Exhaust System

a. Exhaust manifold or muffler restricted causing back pressure
a. Clean or replace manifold and muffler

ROUGH ENGINE IDLE

1. Carburetor

a. Improper idling adjustment
a. Adjust according to instructions

b. Carburetor float needle valve not seating
b. Clean or replace

2. Air Leaks

a. Carburetor to manifold heat insulator or gasket leaks
a. Tighten carburetor to manifold bolts or replace heat insulator or gasket

b. Manifold to head gasket leaks
b. Tighten manifold to head bolts or replace gaskets

c. Air leaks in windshield wiper vacuum line
c. Check for leaks and repair

3. Valves

a. Improper lash adjustment
a. Check and adjust valves

b. Valves not seating properly
b. Grind valves

c. Valves loose in guides or bores
c. Condition valves

4. Cylinder Head

a. Cracks in exhaust ports
a. Replace cylinder head

b. Head gasket leaks
b. Replace cylinder head gasket

ENGINE MISSES ON ACCELERATION

1. Carburetion

a. Accelerating pump jet misadjusted plugged or vapor vent ball in pump plunger not working
a. Overhaul carburetor or, on eight cylinder models, adjust pump travel.

b. Lean fuel mixture
b. Overhaul carburetor

2. Ignition Trouble

a. Faulty spark plugs
a. Clean, adjust or replace plugs

b. Faulty ignition wiring
b. Replace faulty wiring

c. Improperly adjusted or faulty distributor points
c. Adjust or replace distributor points

d. Weak coil
d. Replace coil

3. Engine

a. Burned or improperly adjusted valves
a. Adjust, replace or grind valves

b. Leaky manifold gaskets
b. Tighten manifold or replace gaskets

c. Poor compression due to cylinder, piston or ring condition
c. Overhaul engine

d. Leaky cylinder head gasket
d. Replace gasket

ENGINE NOISE

1. Crankshaft Bearings Loose

a. Bearings improperly fitted
a. Readjust main bearings

b. Crankshaft journals out-of-round
b. Replace or recondition crankshaft

c. Crankshaft journals rough
c. Replace or recondition crankshaft

d. Oil passages in block restricted
d. Clean passages

e. Insufficient oil
e. Adjust or replace bearings. Replenish oil

f. Improper grade and viscosity oil being used
f. Adjust bearings and change to correct oil

g. Oil pump failure
g. Replace oil pump, adjust or replace bearings and other damaged parts

h.Contaminated oil
h. Wash motor thoroughly. Adjust or replace bearings and other damaged parts

2. Connecting Rod Bearings Loose

a. Worn bearings
a. Replace bearings

b. Crankpins rough
b. Polish or replace shaft. Adjust or replace bearings

c. Insufficient oil
c. Adjust or replace bearings and replenish oil

d. Oil pump failure
d. Replace oil pump. Replace or adjust rod bearings

e. Improper grade and viscosity of oil used
e. Replace rod bearings and change to proper oil

3. Pistons or Pins Loose

a. Excessive cylinder wear
a. Hone cylinders and fit new pistons and rings. Make sure all abrasive that would cause cylinder wear is removed.

b. Improperly fitted pistons or pins
b. Replace pistons or pins

c. Contaminated oil
c.Make necessary replacements, flush oiling system and use new oil

d. Faulty fuel or ignition system causing unburned fuel to flush the oil from cylinder walls
d. Make necessary repairs to fuel or ignition system, replace worn parts and change oil

e. Piston pin or bore wear
e. Ream pin bore and install oversize piston pins on six cylinder models. Replace pistons and pins on eight cylinder models

4. Engine Noise-General

a. Bent connecting rod
a. Replace rod

b. Excessive end play in camshaft on six cylinder models
b. Replace camshaft thrust plate, or correct end play by pressing gear on further

c. Excessive crankshaft end play
c. Replace main bearings

d. Broken piston ring
d. Replace broken ring and check condition of cylinder wall

e. Loose timing gears or chain
e. Replace timing gears or chain

f. Dry push rod sockets
f. Polish and lubricate push rod sockets

g. Bent oil gauge rod
g. Replace oil gauge rod

h. Improperly adjusted valve lash
h. Adjust valve lash

i. Sticking valves
i. Free or grind valves

General Information 


                        SIX CYLINDER ENGINE
---------------------------------------------------------------------

Type                        Valve-in-Head

Number of Cylinders         In-line 6 
Lubrication                 Full Pressure
Piston Displacement         235.5 cu. in.
Bore                        3 9/16" 
Stroke                      3 15/16" 
Compression Ratio           8.0:1
Horsepower (S.A.E.)         30.4
Firing Order                1-5-3-6-2-4



---------------------------------------------------------------------

                             Cylinder Block

Material                    Cast Alloy Iron 
Bore                        3.5620"-3.5640" 



---------------------------------------------------------------------

                             Crankshaft and Bearing 

Material                    Drop-Forged Steel 
Stroke                      3  15/16"±.005" 
Main Bearings 
   Number                   4
   Type                     Precision 
   Size    
      Front                 2.6835"-2.6845"  
      Front Intermediate    2.7145"-2.7155" 
      Rear Intermediate     2.7455"-2.7465" 
      Rear                  2.7765"-2.7775"
    End Clearance            .003"-.009" 
      Runout at 
      Intermediate Bearing   .002" Max. 
   Main Bearing Clearance 
      New                    .001"-.003" 
      Used                   .001"-.004" 
      Undersize Bearings     .002"-.010".020"-.030"
Connecting Rod Bearing Journal 
   Diameter                  2.311"-2.312" 



---------------------------------------------------------------------

                      Camshaft and Bearings

Material                     Cast Alloy Iron 
Bearings 
   Material                  Steel-Backed Babbitt 
   Number                    4
Journal Diameter 
   Front                     2.1537"-2.1547" 
   Front Intermediate        2.0912"-2.0922" 
   Rear Intermediate         2.0287"-2.0297" 
   Rear                      1.9662"-1.9672" 
   Clearance                  .0015"-.0035" 
Runout at Intermediate 
   Bearing                    .002" 
Drive 
   Type                       Helical Gear 
   Camshaft Driven Gear       Composition 
   Crankshaft Drive Gear      Steel 
   Back Lash                  .003"-.005"



---------------------------------------------------------------------

                          Connecting Rods and Bearings
                                 235 Engine

Material                      Drop-Forged Steel 
Width at Crank Pin            1/123"-1/129" 
Width at Crank Pin            1.2415"-1.2435" 
Upper Bearing                 Locked on Pin 
Lower Bearing                 Precision Insert 
   Material                   Steel-Backed, Thin Wall Babbitt 
   Bore Diameter              2.3127"-2.3188" 
   Clearance on Diameter
       New                     .001"-.003" 
       Used                    .001"-.004" 
   Side clearance              .005"-.012" 
   Torque, Oiled Threads       35-45 ft. lbs. 
   Center to Center Length     6.81" 
   Undersize Bearings          .001"-.002"-.010"-.020"



---------------------------------------------------------------------

                     Pistons, Pins and Rings

Piston 
   Pin Offset                  5/64" 
   Material                    Cast Alloy Aluminum 
                               Steel Struts 
   Skirt Clearance             .0005"-.0011" 
                              7 lbs. to 18 lbs. pull, .0015 feeler 
Oversize                      High Limit Standard 
                              .020"-.030"-.040" 
Pin 
   Material                    Chromium Steel 
   Diameter                   .8660"-.8665" 
   Oversize                   .0015"-.003"-.005" 
   Fit                        Slip 
   Max. Taper                 .0002" 
   Clearance                  .00015"-.00025" 
Compression Rings             .00015"-.00025" 
   Type                       Twist 
   Number                     2
   Material                   Cast Iron 
   Width                     .0930"-.0935" 
   Gap Clearance             .007"-.020" 
   Ring Clearance in Groove  .001"-.003" 
Oil Control Ring
   Material                   Steel 
   Type                       2 Crome Plated Rails, Spacer
   Width                     .181"-.188 
   Gap Clearance             .015"-.055"  ( on Rails )
   Ring Clearance in Groove  .000"-.008" 
   Expander Type              Segmented Steel
   Oversize Rings            .020"-.030"-.040"



---------------------------------------------------------------------

                     Cylinder Head and Valves

Head 
   Material                   Cast Alloy Iron 
   Bolt Torque                90-95 ft. lbs.  ( Oiled Threads )
Inlet Valves    
   Material                   Silchrome or Nickel Chrome Steel 
   Seat Angle                 30° on valve, 31° on seat 
   Dia. Head                  1 7/8" 
   Length                     6.364"-6.394" 
   Stem Dia                    .3410"-.3417" 
Valve Lash, Hot                .006" (with solid lifters) 
Exhaust Valves 
   Material                   Conventional Silchrome XB 
                              Powerglide Silchrome XCR Steel 
   Seat Angle                 45° 
   Dia. Head                  1 1/2" 
   Length                     4.905"-4.930" 
   Stem Dia                    .3410"-.3417" 
   Valve Lash, Hot             .013" 
Valve Stem Guides 
   Clearance 
      Inlet                    .001"-.0027" 
      Exhaust                  .001"-.0027" 
Oversize Valve Stems           None
Ream 
   Inlet                       .3427"-.3437" 
   Exhaust                     .3427"-.3537" 
Extend Above Head
   Inlet                       1.00"-1.015" 
   Exhaust                     .935"-.950"
Length 
   Inlet                       3.335" 
   Exhaust                     2.430"
Valve Seats 
   Angle 
      Inlet                    31° 
      Exhaust                  46° 
   Dia. Cutter 
      Inlet                    1.978"-1.998" 
      Exhaust                  1.5525"-1.5725" 
   Width in Head 
      Inlet                    .035"-.060" 
      Exhaust                  .062"-.093" 
Valve Springs 
   Free Length                 2 5/32" (conventional) 
                               2 15/64" (Powerglide)
   Lbs. Pressure at Valve-     
      Open Length              155-165 lbs. at 1.505" 
                                (Conventional)
                               194-210 lbs. at 1.462 (Powerglide)   
Installed Height               1 51/64" to 1 55/64" 
Valve Rocker Cover
      Nut Torque             25 ft. lbs. ( Maximum )


---------------------------------------------------------------------

                             Oil Pump

Type                           Spur Gear 
Pressure                       35 psi 



---------------------------------------------------------------------

                             Clutch Housing Pilot Hole

Runout                        .008" Max. 



---------------------------------------------------------------------

                             Flywheel
Runout                       .008" Max. 

General Information 


                        EIGHT CYLINDER ENGINE 
---------------------------------------------------------------------

Type                        Valve-in-Head 

Number of Cylinders         V-8 
Lubrication                 Full Pressure 
Piston Displacement         265 cu. in. 
Bore                        3 3/4" 
Stroke                      3" 
Compression Ratio           8.0:1 
Horsepower (S.A.E.)         45  
Firing Order                1-8-4-3-6-5-7-2 



---------------------------------------------------------------------

                             Cylinder Block

Material                    Cast Alloy Iron 
Bore                        3.7495"-3.7515" 



---------------------------------------------------------------------

                             Crankshaft and Bearing 

Material                    Drop-Forged Steel 
Stroke                      3"±.005" 
Main Bearings 
   Number                   5 
   Type                     Precision 
   Size    
      Front                   
      Front Intermediate    All Journals 
      Rear Intermediate     2.2978"-2.2988" 
      Rear                  
    End Clearance            .002"-.006" 
      Runout at 
      Intermediate Bearing   .002" Max. 
   Main Bearing Clearance 
      New                    .00l"-.003" 
      Used                   .00l"-.004" 
      Undersize Bearings     .001"-.002"-.010"-.020" 
Connecting Rod Bearing Journal 
   Diameter                  1.999"-2.000" 



---------------------------------------------------------------------

                      Camshaft and Bearings

Material                     Cast Alloy Iron
Bearings 
   Material                  Steel-Backed Babbitt 
   Number                    5
Journal Diameter 
   Front                      
   Front Intermediate        All Journals 
   Rear Intermediate         1.8682"-1.8692"
   Rear                       
   Clearance                  .0015"-.0035" 
Runout at Intermediate 
   Bearing                    .002"
Drive 
   Type                       Silent Link Chain and Sprocket 
   Camshaft Driven Gear       Alloy Cast Iron 
   Crankshaft Drive Gear      Steel 
   Back Lash                  



---------------------------------------------------------------------

                          Connecting Rods and Bearings
                                     235 Engine

Material                      Drop Forged Steel 
Width at Crank Pin            1.011"-1.007"
Width at Crank Pin            .944"-.945"
Upper Bearing                 Pin Pressed into Rod
Lower Bearing                 Precision Insert
   Material                   Steel-Backed, Thin Wall Babbitt
   Bore Diameter              2.1247"-2.1252"
   Clearance on Diameter
       New                     .001"-.003"
       Used                    .001"-.004"
   Side clearance              .008"-.014"-on Two Rods
   Torque, Oiled Threads       30-35 ft. lbs.
   Center to Center Length     5.700"
   Undersize Bearings          .001"-.002"-.010"-.020"



---------------------------------------------------------------------

                     Pistons, Pins and Rings
Piston 
   Pin Offset                  5/64" 
   Material                    Cast Alloy Aluminum 
                               Steel Struts 
   Skirt Clearance             .0005"-.0011"
                              7 lbs. to 18 lbs. pull, .0015 feeler 
Oversize                      High Limit Standard
                              .020"-.030"-.040" 
Pin 
   Material                    Chromium Steel 
   Diameter                   .9270"-.9273" 
   Oversize                   None
   Fit                        Shrink in rod, slip in Piston
   Max. Taper                 .0002"
   Clearance                  .00015"-.00025" 
Compression Rings       
   Type                       Twist
   Number                   2
   Material                  Cast Iron
                                  Top Ring Chrome Flashed

   Width                     .077"-.078"
   Gap Clearance             .007"-.020"
   Ring Clearance in Groove  .001'-.003"
Oil Control Ring
   Material                   Steel 
   Type                       2 Crome Plated Rails, Spacer
   Width                     .181"-.188 
   Gap Clearance             .015"-.055"  ( on Rails )
   Ring Clearance in Groove  .000"-.008" 
   Expander Type              Segmented Steel
   Oversize Rings                .020"-.030"-.040"
Valve Rocker Cover
      Nut Torque                25 ft. lbs. ( Maximum )


---------------------------------------------------------------------

                    Cylinder Head and Valves

Head 
   Material                   Cast Alloy Iron 
   Bolt Torque                60-70 ft. lbs. 
Inlet Valves    
   Material                   Silchrome or Nickel Chrome Steel 
   Seat Angle                 45° on valve 
   Dia. Head                  1.720"
   Length                     4.902"-4.922" 
   Stem Dia                    .3415"-.3422" 
Valve Lash, Hot                .008" (solid lifters) 
Exhaust Valves 
   Material                   Conventional Silchrome XB 
                              XCR Steel 
   Seat Angle                 45° valve, 46° seat 
   Dia. Head                  1 1/2"
   Length                     4.913"-4.933" 
   Stem Dia                    .3410"-.3417"
   Valve Lash, Hot             .016' with solid lifters 
Valve Stem Guides 
   Clearance 
      Inlet                    .001"-.0027" 
      Exhaust                  .015".032" 
Oversize Valve Stems           .003"-.015"-.030"
Ream 
   Inlet                       .3432"-.3442"
   Exhaust                     .3432"-.3442"
Extend Above Head
   Inlet                       No replaceable guides
   Exhaust                     
Length 
   Inlet                       No replaceable guides
   Exhaust                  
Valve Seats 
   Angle 
      Inlet                    46°
      Exhaust                  46°
   Dia. Cutter 
      Inlet                    1.770"-1.790"
      Exhaust                  1.550"-1.570"
   Width in Head 
      Inlet                    .035"-.060"
      Exhaust                  .062"-.093"
Valve Springs 
   Free Length                 2.03"
   Lbs. Pressure at Valve-     
      Open Length              71 to 79 lbs. at 1 45/64"
   Installed Height            1 11/16" to 1 47/64"



---------------------------------------------------------------------

                             Oil Pump

Type                           Spur Gear
Pressure                      35 psi



---------------------------------------------------------------------

                             Clutch Housing Pilot Hole

Runout                        .008" Max



---------------------------------------------------------------------

                             Flywheel

Runout                      .008" Max