Section VI. CYLINDER BLOCK

k. Install the governor lever and related parts

j. Install the breaker points, carburetor, fuel

(items 1 through 6, fig. 4-11). Adjust the engine

tank and lines. muffler, and air cleaner (TM 5 -

breaker points and governor (TM 5-4320-259-12).

4320-259-12).

Section VI. CYLINDER BLOCK

in full contact with the walls. Use diesel fuel or

4-19. Description

kerosene as a cutting and cooling agent.

a. The cast iron cylinder block includes the

(2) With the lower end of the hone alined with

cylinder and crankcase. The valves seat in valve

the lower end of the cylinder, start the rotation of

seat inserts which are pressed into the top of the

the hone. Move the hone up and down continuously

cylinder block. Valve tappets and valve stems ride

during reboring to prevent the formation of ridges.

in bores in the cylinder block. The exterior of the

Check the size frequently.

cylinder is deeply finned to provide efficient air

(3) When the bore is within 0.0025 inch of

cooling of the cylinder, dispelling the heat of

desired size, remove the coarse stones and replace

combustion of the burning gases in the cylinder.

with the burnishing stones. Continue to rebore with

b. One side of the cylinder block is bored to

the burnishing stones until the bore is within

provide seats for the shaft seal and the ball bearing

0.0005 inch of the desired size. Change stones and

in which the crankshaft rides. The opposite side of

use finish stones to polish the bore to the desired

the cylinder block is open and provides mounting

size.

facilities for the bearing plate. The bottom of the

(4) After reboring, clean the cylinder walls

cylinder block is open and provides mounting

with soap and water. Dry thoroughly. Apply a light

facilities for the oil pan.

coat of SAE 10 engine oil to prevent rust.

d. Make sure the valve seats meet the

4-20. Removal

requirements given in paragraph 4-5 g and h. If the

a. Remove the air cleaner, muffler, fuel tank and

valve seat inserts are cracked or damaged beyond

lines, carburetor, breaker points, flywheel, and

repair, new inserts (21 and 22, fig. 4-7) can be

magneto (TM 5-4320-259-12).

installed. When installing new inserts, heat the

b. Remove the centrifugal pump from the engine

engine cylinder block in an oven to about 200 F.

(para 3-2).

Chill the valve seat inserts with dry ice. The chilled

c. Remove the cylinder head and valves (para 4-

inserts should press easily into the valve seat insert

4).

counterbores in the heated cylinder block. Make

d. Remove the piston and connecting rod (para

sure the counterbores are thoroughly cleaned before

4-8).

installing the inserts, otherwise the valves will not

e. Remove the main bearings and crankshaft

seat properly. The valves must be lapped into the

(para 4-12).

replaced inserts. Refer to paragraph 4-5 h.

f. Remove the camshaft and governor (para 4-

16).

4-22. Reassembly

a. Install the camshaft and governor parts (para

4-21. Cleaning and Inspection

4-18).

a. Clean the cylinder block thoroughly with an

b. Install the main bearings and crankshaft

approved cleaning solvent; dry thoroughly.

(para 4-14).

b. Inspect the cylinder block for cracks,

c. Install the piston and connecting rod (para 4-

damaged threads, cracked cooling fins, scored

10).

cylinder bore, and damaged bearing and seal seats.

d. Install the valves and cylinder head (para 4-

c. Check the cylinder bore for an out-of-round

6).

condition. Use an inside micrometer and check at

e. Install the centrifugal pump on the engine

points 90. degrees apart for the full length of the

(para 3-4).

working surface of the cylinder bore. If the cylinder

f. Install the magneto, flywheel, breaker points,

bore is out of round, tapered, or worn beyond the

carburetor, fuel tank and lines, muffler, and air

limits cited in table 4-1, rebore the cylinder as

cleaner (TM 5-4320-259-12).

follows:

g. Service the engine completely and adjust the

(1) Lower the hone into the bore after it is

breaker points and governor (TM 5-4320-59-12).

properly centered. Adjust the stones so that they are

4-11