CHAPTER 11 ENGINE REPAIR INSTRUCTIONS

TM 10-3930-630-34

CHAPTER 11

ENGINE REPAIR INSTRUCTIONS

Section I. CYLINDER HEAD AND VALVES

heavy engine oil through spark plug hold to seal pistons

11-1. Description

and repeat test.

a. The cylinder head is an alloy cast iron unit

(1) To check piston blow-by, remove engine oil filler

secured to the engine block with special hardened studs

cap. Crank engine, and as the piston is slowly brought

and screws. The head seals the top end of the cylinders

to compression listen at the oil filler tube. If piston is

to form the combustion chambers, and has passages for

allowing air to leak past, it can be heard.

the intake of the air-fuel mixture, and the expulsion of

(2) Mark cylinder for piston repair.

exhaust gases, as well as cored passages through which

the coolant flows to prevent overheating.

11-3. Valve

Mechanism,

Removal

and

b. The cylinder head as well as the valve tappet

cover must be removed to gain access to the valves

Disassembly

and valve springs. The end of each valve stem is fitted

NOTE

with a shallow steel retainer that surrounds the end of

The

valve

mechanism

the valve spring, and is held to the stem by a pair of

disassembled

the

removal

wedge keepers or locks.

procedure.

a. Refer to TM 10-3930-630-12 and remove the

11-2. Cylinder Compression Check

cylinder head.

a. Refer to TM 10-3930-630-12 and remove spark

b. Remove the valve locks, valve springs,

plugs and check compression in each cylinder using a

retainers, valves and valve springs as illustrated in

compression tester and gage. Crank engine to check

figure 11-2.

compression.

TA067440

Figure 11-1. Checking cylinder compression.

b. Note reading on each cylinder. Pressure of

cylinders must be within 10 psi (0.703 kg/cm2) of each

other.

c. Note cylinders that vary from tolerance. These

cylinders will have to be repaired.

d. If it is suspected that compression may be

Figure 11-2. Values, removed and installation .

leaking past piston rings, inject small amount of

c. After valves are removed, remove tappets (9),

fig.11-2A.

11-1