Cleaning and Inspection - TM-10-3930-632-340093

TM 10-3930-632-34

twice the number of teeth as the crankshaft gear so that

Inspect the camshaft end plug in the cylinder

the camshaft rotates at one-half the speed of the

block. Replace if any leaking is evident from the

crankshaft. The camshaft has eight cam lobes, two for

circumference of the plug.

each set of valves. The cam lobes are positioned to

Inspect the camshaft bearings in the cylinder

provide the correct valve opening and closing

block for scoring or visible damage; replace damaged

characteristics for each valve. The camshaft is provided

bearings if necessary. Check the camshaft-to-bearing

with an integral gear which drives the engine oil pump.

clearance, and, if necessary, replace bearings as

The camshaft rides in sleeve bearings which are seated

follows:

in the cylinder block.

(1) Temporarily insert the camshaft in the block.

Check the clearance between the camshaft bearing

journals and camshaft bearings with feeler stock cut in

9-35.

Removal

strips s inch wide. Dress the feeler stock with a stone

to eliminate burrs or feathered edges.

Clearance

With the engine removed from the truck and

between the fan end and drive end bearings and journals

mounted on an engine stand, proceed as follows:

must be between 0.002 and 0.004 inch and the center

Remove the cylinder head (para 9-6).

journal must be between 0.003 and 0.0047.

Remove the valves and valve tappets (para 9-

11).

CAUTION

Remove the gear cover (para 9-19).

Remove the governor parts.

Do not insert the camshaft too far into the block.

Pull the gear (11, fig. 9-6) from the camshaft

If the camshaft bumps the expansion plug on the

(17).

drive end of the engine, an oil leak could result.

Remove the two bolts (12) and lockwashers

(13) that secure the thrust plate (14) to the block; remove

(2) If clearance exceeds tolerances, remove the

the thrust plate.

camshaft and remove the camshaft bearings. New

Pull the camshaft (17) from the block.

bearings are pre-reamed. Install new bearings, taking

care to align the oil holes with the passages in the block.

WARNING

Use caution to prevent damage to the bearings during

installation.

Dry cleaning solvent P-D-680 is toxic and

flammable. Wear protective goggles and gloves

9-37.

Installation

and use only in a well ventilated area. Avoid

Lubricate the camshaft bearings with engine

contact with skin, eyes, and clothes and don't

oil and install the camshaft in the block. Position the

breathe vapors. Do not use near open flame or

excessive heat. The flash point is 100F -

thrust plate (14, fig. 9-6) on the camshaft; secure with

the two bolts (12) and lockwashers (13).

138F. (38C - 59C). If you become dizzy while

Hold the camshaft toward the front of the

using cleaning solvent, get fresh air immediately

engine with a bar inserted into the fuel pump hole. Align

and get medical aid. If contact with eyes is

the timing marks on the camshaft and crankshaft gears

made, wash your eyes with water and get

(fig. 9-30) and drive the gear (11, fig. 9-6) onto the

medical aid immediately.

camshaft. Position the governor drive assembly against

the camshaft gear and secure with nut (10, fig. 9-6).

9-36.

Cleaning and Inspection

Tighten the nut to 85 to 90 ft/lbs torque.

Clean all parts with cleaning solvent P-D-680

and dry thoroughly.

Inspect the camshaft for cracks, worn or

scored cams, worn or scored bearing surfaces, chipped,

cracked, or broken gear teeth, and clogged oil passages.

Refer to table 9-1 for wear limits. Replace a damaged

camshaft.

Inspect the' thrust washer for scoring and

wear. Replace the thrust washer if any signs of wear are

evident.

Inspect the cam gear for cracked, chipped or

broken gear teeth, damaged shaft bore, or worn thrust

surface. The cam gear and the mating gear on the

crankshaft must be replaced as a pair. Do not attempt to

Figure 9-30. Timing Gears Showing Alignment Marks.

replace these gears singly.

Change 1 9-24