CHAPTER 6 REPAIR OF ENGINE

TM 10-3930-633-34

CHAPTER 6

REPAIR OF ENGINE

Section I. DESCRIPTION

6-1. General

the left side of the engine, toward the front. The

distributor is gear driven from the camshaft and,

The engine is a six cylinder, in-line, overhead

in turn drives the oil pump through an in-

valve design. Engine displacement is 300 cubic

termediate drive shaft.

inches. The engine is equipped with a 12-volt

b. The crankshaft is supported by four main

electrical system, including a coil and distributor

bearings, with the thrust being controlled by

t y p e ignition system, starting system, and

flanges on the number 3 main bearing. The

battery charging system with alternator. The fuel

pistons are tin-plated aluminum alloy and have

system includes the mechanically operated fuel

two compression rings and one oil control ring.

pump and single throat, down-draft carburetor.

Description of these systems is provided under

6-5. Lubrication System

separate chapter headings in this manual.

a. The lubrication system is a positive pressure

6-2. Cylinder Head

system and is supplied by a rotor type pump

submerged in the crankcase sump. A spring

The cylinder head carries the valves, rocker

loaded relief valve in the pump limits the

arms and springs, manifold assemblies, coolant

maximum pressure of the system. Oil relieved by

outlet, and thermostat. Valve guides are integral

the valve is directed back to the intake side of the

with the head. Refer to Section IV for cylinder

pump.

head repairs.

b. All the oil discharged by the pump passes

6-3. Valves

through a full flow type filter before entering the

a. Valve Timing. Valve timing and operation

engine. The filter has an integral bypass valve

is a c c o m p l i s h e d by the camshaft, lifters,

and mounting gasket. The by-pass valve permits

pushrods, and rocker arms. The camshaft is

oil to by-pass the filter if it becomes clogged with

driven from the crankshaft by a timing chain and

impurities. thereby maintaining an emergency

sprockets, enclosed in a cover on the front of the

supply of oil to the engine at all times. An an-

engine. The camshaft is supported by four steel-

tidrain back diaphragm prevents the reverse flow

backed babbitt bearings pressed into the block.

cf oil from the upper engine parts whenever the

Camshaft thrust is controlled by a thrust washer

engine is stopped.

located between the camshaft sprocket and the

c. From the filter, the oil flows into the main oil

front camshaft journal. An integral eccentric on

gallery, which supplies oil to all the camshaft and

the camshaft operates the fuel pump.

main bearings through a drilled passage in each

b. Valve Train. The lifters are of the ex-

bearing web. The timing gears receive oil through

panding hydraulic type, where oil under pressure

a squirt hole in the block face. Oil slingers prevent

is used to expand the lifter to remove all valve

leakage by directing oil away from the crankshaft

lash from the mechanism. Pushrods are tubular,

front. and rear oil seals.

steel, with oil-cushioned sockets. Intake and

d. Cylinder walls, pistons, and piston pins are

exhaust valve assemblies are of the rotating type.

lubricated through a drilled passage in each

6-4. Cylinder Block

connecting rod journal of the crankshaft. Drilled

passages in the block supply pressurized oil to the

a. The cylinders are numbered from 1 to 6

hydraulic lifters, pushrods and rocker arms. The

starting at the front of the engine. The firing

oil in the pushrod chamber drains back into the

order is 1-5-3-6-2-4. `The distributor is located on

pan through cored openings in the cylinder block.

6-1