Figure 4-15. Removing upper bearing shell with angular pin.

TM 5-4320-234-34

(4) Inspect the bearing shells for cracks and

scoring. New bearings are smooth and highly polished.

After a few hours of operation, the bearing surfaces

become leaden grey in color and develop minute craters

which give the bearing surfaces an almost cellular

appearance. This is a natural characteristic of the

bearing and does not indicate bearing failure. Replace

bearings if they are scored or damaged. Check the

bearing thickness with a ball micrometer. Check several

locations on the bearing. If thickness is less than 0.0920

inch (0.2300 cm), replace the bearing.

(5) Inspect the bearing caps for cracks and

distortion and for burrs and gouges of the seating

surfaces. Clean up any burrs with a fine stone to ensure

proper seating of the bearing cap on the block.

Figure 4-15. Removing upper bearing shell with

c. Reassembly and Installation.

angular pin.

(1) Install the rear oil seal and oil guard as

directed in paragraph 4-5c.

(7) Pull the gear (21, fig. 4-13) from the

(2) Position the thrust plate (23, fig. 4-13) on

crankshaft (36). Remove the key (22) and the thrust

the crankshaft and install the key (22) in the keyway of

plate (23).

the crankshaft, after you make sure that the keyway is

b. Cleaning and Inspection.

free of burrs. Press the gear (21) onto the crankshaft.

WARNING

CAUTION

Clean all parts in a well-ventilated area.

When you install the crankshaft, make sure

Avoid inhalation of solvent fumes and

that you aline the timing marks on the

prolonged exposure of skin to cleaning

crankshaft with the timing marks on the

solvent. Wash exposed skin thoroughly.

camshaft gear. See paragraph 4-11.

Dry cleaning solvent (Fed. Spec. P-D-680)

used to clean parts is potentially dangerous

(3) Position the upper half of the main

to personnel and property. Do not use near

bearings (27, 30, 33, and 35) in the seats in the

open flame or excessive heat. Flash point of

crankcase. Position the crankshaft in the bearing shells.

solvent is 100 F. to 138 F. (38 C. to 59 C.).

(4) Install the lower half of the main bearings

into the bearing caps (25, 29, 32, and 34).

(1) Clean all parts with cleaning solvent (Fed.

(5) Check the clearance between the

Spec. P-D-680). Clean oil passages in the crankshaft

crankshaft bearing journals and bearings as follows:

with a rifle cleaning brush. Make sure all passages are

(a) Place a piece of plastigage near the oil

open.

hole of the bearing cap.

(2) Inspect the crankshaft for cracks, worn or

(b) Position the cap on the block and

scored journals, damaged threads, and burred keyways.

secure with the two screws and lockwashers. Tighten

Refer to table 4-1 for wear limits. If magnetic particle

the screws to 85 to 95 foot-pounds (11.75 to 13.13 kgm)

inspection equipment is available, you should use it to

torque.

check the crankshaft for hidden flaws. Replace a

damaged crankshaft.

Check the bearing journal-to-bearing clearance

(3) Inspect the gear for cracked, chipped and

indicated by the plastigage (fig. 4-16).

broken teeth; replace a damaged gear.

4-17