Section V. CYLINDER BLOCK

TM 10-3930-633-34

(7) Check the dividers against a scale. If the

assembled height is greater than the specified

limit (table 6-4), install the necessary 0.030 inch

thick spacer(s) between the cylinder head spring

pad and the valve spring to bring the assembled

height to the recommended dimension. Do not

install spacers unless necessary. Use of spacers in

excess of recommendations will result in over-

stressing the valve springs and overloading the

c a m s h a f t lobes which could lead to spring

breakage and worn camshaft lobes.

Figure 6-22. Checking Valve Spring Height.

Section V. CYLINDER BLOCK

part dry and immediately apply a coating of zinc

6-22. Cylinder Block Cleaning

oxide dissolved in wood alcohol. If cracks are

a. After any cylinder bore repair operation,

present, the coating will become discolored at the

such as honing or deglazing, clean the bore(s)

cracked area. Replace the block if it is cracked.

w i t h s o a p o r detergent and water. Then,

b. Check all machined gasket surfaces for

thoroughly rinse the bore(s) with clean water to

burrs, nicks, scratches and scores. Remove minor

remove the soap or detergent, and wipe the

imperfections with an oil stone. Check the

bore(s) dry with a clean, lint-free cloth. Finally,

cylinder block for flatness of the cylinder head

wipe the bore(s) with a clean cloth dipped in

gasket surface following the procedure and

engine oil. If these procedures are not followed,

specifications recommended for the cylinder head.

rusting of the cylinder bore(s) may occur.

The cylinder block can be machined to bring the

b. If the engine is disassembled, thoroughly

cylinder head gasket surface within the flatness

clean the block in solvent. Remove old gasket

specifications, but not to exceed 0.010 inch stock

material from all machined surfaces. Remove all

removal from the original gasket surface.

pipe plugs that seal oil passages; then clean out

c. Replace all expansion-type plugs that show

all the passages, Blow out all passages, bolt

evidence of leakage. See paragraph 6-25.

holes, etc., with compressed air.

d. Inspect the cylinder walls for scoring,

c. Make sure the threads in the cylinder head

roughness, or other signs of wear. Check the

bolt holes are clean. Dirt in the threads may cause

cylinder bore for out-of-round and taper. Measure

binding and result in a false torque reading. Use a

the bore with an accurate bore gage following the

t a p to true-up threads and to remove any

instructions of the manufacturer. Measure the

deposits.

diameter of each cylinder bore at the top, middle

6-23. Cylinder Block Inspection

and bottom with the gage placed at right angles

a. After the block has been thoroughly cleaned,

and parallel to the centerline of the engine (fig. 6-

check it for cracks. Minute cracks not visible to

23). Use only the measurements obtained at 90

the naked eye may be detected by coating the

degrees to the engine centerline when calculating

suspected area with a mixture of 25 percent

the piston to cylinder bore clearance.

kerosene and 75 percent light engine oil. Wipe the

6-21