ENGINE REPAIR AND ASSEMBLY.

TM 10-3930-623-34

7. Install oil slinger (4) and drive coupling on

7. Sandblast, wire brush, or sandpaper remaining

crankshaft with screw (2).

paint or rust from the surface being worked. Rinse with

paint thinner.

8. Check crankshaft end play for 0.002 to 0.006

inch clearance. See figure 7-1. If clearance is not within

PAINT APPLICATION. Apply paint in

6-13.

specification, replace front main bearing. Flanges on

conformance with good commercial practices and the

this bearing determine endplay.

applicable requirements of Military Specification MIL-T-

704.

6-17. CRANKSHAFT CLEARANCE. Check crankshaft

clearance as follows after new bearings have been

6-14. ENGINE REPAIR AND ASSEMBLY.

installed.

6-15. CRANKSHAFT REPAIR.

1. Remove bearing cap and place a piece of 0.002

by 1/2 by 1 inch shim stock in bearing cap (see 20,

1. If crankshaft journals do not conform to the

figure 7-1).

specifications in figure 7-1, or are badly scored, grind

2. Install bearing cap and tighten to 85 to 95 foot-

journal to next standard undersize; and, use undersize

pounds torque. If crankshaft rotates with noticeable

bearings.

drag, clearance is correct.

NOTE

3. Clearance may be checked by "Plastigage"

Check the crankshaft for straightness

method if "'Plastigage" and special measuring scale are

within 0.002 inch TIR before grinding.

available. if this method is used, do not rotate crankshaft

Maximum grinding is limited to 0.020

with "Plastigage" in place.

inch less than diameter shown in

NOTE

figure 7-1 for standard crankshaft.

Install and check one bearing cap at

a time.

2. After grinding crankshaft, check crankshaft for

required fillet radii as follows:

6-18. PISTON FIT. Check each piston without rings for

clearance in respective cylinder bores.

Check as

a. Connecting rod and all except main rear

follows:

journal 5/64 to 7/64 inch.

NOTE

b. Main rear journal 7/64 to 9/64 inch.

Piston and cylinder walls must be

perfectly clean and dry when fitting

3. Grind new fillet radii if required.

pistons. Pistons and block should be

at room temperature (68 deg - 70 deg

6-16. CRANKSHAFT INSTALLATION.

F ) when checking.

1. Install one-half of each main bearing insert ( 4,

1. Insert inverted piston in cylinder with long strip of

35 and 36, figure 4-28) in correct place in block. Oil

1/2 inch wide 0.002 inch feeler stock between the piston

each insert with OE-30 motor oil.

and cylinder wall, midway between the piston and

cylinder wall, midway between piston pin bosses. Piston

NOTE

pin bosses align with crankshaft.

Machined surface in block, into

2. Slide piston into cylinder until skirt is 2 inches

which insert fits, must be wiped

below deck.

thoroughly clean of foreign particles

3. Attach spring scale to feeler stock and pull scale

so that bearing heat will be

and feeler stock evenly from cylinder. Proper fit requires

transferred directly to block web.

5-to-10-pound pull. (See figure 6-2).

2. Lay crankshaft (37) in place in block, install

6-19. PISTON RING FIT. Check piston ring for side

remaining insert halves in correct main bearing caps (25,

clearance in piston groove and end gap in cylinder as

26, 27 and 28) and reinstall caps, loosely.

shown in figure 7-1. If not within specifications, increase

end gap with a piston ring file. If groove clearance is

3. Check bearing clearance, see paragraph 6-18.

below specifications, rub ring on a flat piece of fine

4. After clearance has been checked, torq ue main

emery cloth until clearance is obtained.

bearing cap screws (32 and 33) to 84-95 foot-pounds.

NOTE

5. Install crankshaft gear (5) and key (6) on

Check piston for unremoved carbon

crankshaft.

buildup in grooves before reducing

ring thickness.

6. Assemble hydraulic pump drive coupling and

gear (1) with retaining ring (3).

6-3