Reassembly and Installation - TM-10-3930-632-340091

TM 10-3930-632-34

inspection equipment is available, use it to check the

NOTE

crankshaft for hidden flaws.

Replace a damaged

Upper main bearing shells can be removed

crankshaft.

without removing the crankshaft. To remove the

Inspect the gear for cracked, chipped and

upper shell, remove the main bearing cap at the

broken teeth; replace a damaged gear.

defective bearing and remove the lower bearing

Inspect the bearing shells for cracks and

shell. Insert a pin with an angular head in the oil

scoring. New bearings are smooth and highly polished.

hole of the crankshaft as shown in figure 9-27.

After a few hours of operation, the bearing surfaces

Rotate the crankshaft and roll the bearing shell

become leaden grey in color and develop minute craters

from the cylinder block.

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.

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 assure

proper seating of the bearing cap on the block.

9-33.

Reassembly and Installation

Flatten the seal (26, fig. 9-26) with a hammer

or vise; install in the rear guard (fig. 9-15). Trim the seal

flush with the guard. Install the felt and the assembled

seal and guard in the engine block. Lubricate the seal

with engine oil.

Install the keys (7, fig. 9-20) in the keyways of

the crankshaft, after making sure that the keyways are

free of burrs. Press the thrust plate (9) and gear (6) onto

the crankshaft. Install the slinger (5).

Position the upper main bearing shells (13) in

the seats in the crankcase. Position the crankshaft in

Figure 9-27. Removing Upper Bearing Shell with

the bearing shells.

Angular Pin.

CAUTION

Pull the slinger (5, fig. 9-20), gear (6), and

When installing the crankshaft, make sure the

thrust plate (9) from the crankshaft (26). Remove the

timing marks on the crankshaft gear are aligned

keys (7).

with the timing marks on the camshaft gear.

See paragraph 9-37.

WARNING

Install the lower half of the bearing shells in the

Dry cleaning solvent, P-D-680, used to clean

bearing caps.

parts is potentially dangerous to personnel and

Check the clearance between the crankshaft

property. Avoid repeated and prolonged skin

bearing journals and bearing as follows:

contact.

Do not use near open flame or

(1) Place a piece of plastigage near the oil hole

excessive heat. Flash point of solvent is 100 F

of the bearing cap.

- 138 F. (39 C. - 59 C.).

(2) Position the cap on the block and secure

with the two screws and lockwashers. Tighten the

9-32.

Cleaning and Inspection

screws to 85 to 95 ft/lbs torque.

Clean all parts with cleaning solvent P-D-680.

(3) Remove the bearing and bearing cap.

Check the bearing journal-to-bearing clearance indicated

Clean oil passages in the crankshaft with a rifle cleaning

by the plastigage (fig. 9-28)

brush. Make sure all passages are open.

Inspect the crankshaft for cracks, worn or

scored journals, damaged threads, and burred keyways.

Refer to table 9-1 for wear limits. If magnetic particle

9-22