Reassembly and Installation - TM-10-3930-632-340088

TM 10-3930-632-34

that the bearing surface has an almost cellular

(2) Position a connecting rod in its piston. Install

appearance. This is normal, and is not an

the piston pin; secure with the piston pin retainer ring

indication of impending bearing failure

(14, fig. 9-20).

e. Slide the piston rings (12) squarely into the

Inspect all other parts for cracks, scoring,

cylinders in which they will be used. Check the ring gap

damaged threads, and other damage; replace damaged

with feeler gage. If the ring gap is not at least 0.010 inch,

parts.

file the rings to provide a larger gap. If the ring gap

exceeds 0.020 inch, rebore the cylinders (para 9-41) and

install oversize pistons and rings.

9-29.

Reassembly and Installation

Install a piston ring expander on the bottom ring

a. Check piston fit in the cylinder bore (fig. 9-25)

groove of a piston. Install the piston rings on the piston

using a piece of 0.0015-inch feeler stock cut 1/2 inch

with a standard ring expander tool.

wide. Dress the edges of the feeler stock with a stone to

g. Assemble the remaining pistons, connecting

remove burrs and feathered edges. The block and

rods, and piston rings.

pistons must be at room temperature when piston fit is

h. Install the assembled pistons and connecting

tested. Position the feeler stock midway between the

rods in the same cylinders from which they were

piston pin bosses. With the piston inserted about 2

originally removed. Use a ring compressor to compress

inches into the block, the feeler stock must pull from the

the piston rings. Lubricate the pistons and cylinder walls

block with 5 to 10 pounds pull. If the feeler stock does

with engine oil before installing the pistons. Wrap the

not offer enough resistance, perform the same test with

bottom end of the connecting rods with a cloth to prevent

a new standard size piston. If sufficient resistance is still

damage to the cylinder walls during installation.

not obtained, rebore the cylinders (para 9-41) and install

Check the crank pin bearing journal-to-

oversize pistons.

connecting rod bearing clearance with plastigage. Lay a

piece of plastigage material on the crankshaft journal

and install the connecting rod bearing cap. Torque the

nuts to 35 to 40 ft. lbs. Remove the bearing cap and

compare the width of the flattened plastigage material

with the scale markings on the plastigage package to

determine the clearance.

The bearing-to-journal

clearance shall be 0.0007 to 0.0031 inch. If clearance is

beyond these limits replace the bearing and/or the

crankshaft as required.

As an alternate method of checking crank pin

bearing journal-to-connecting rod bearing clearance,

install a piece of 0.0030-inch thick feeler stock between

the bearing and journal, and install the bearing cap.

Tighten the connecting rod cap bolts to 35 to 40 ft/lbs

torque.

Rotate the crankshaft to detect drag.

clearance is within tolerance, a definite drag will be felt.

Figure 9-25. Checking Piston Fit in Cylinder Bore.

Disassemble the rod cap and remove the shim stock. If

clearance is not within tolerance, replace the connecting

b. If new pistons (15, fig. 9-20) and piston pins

rod bearings and recheck the clearance. If clearance is

(16) are being used, press a new pin bushing (17) into

still not within tolerance, replace the crankshaft.

each connecting rod (21). Ream and hone the sleeve

k. Lubricate the crank pin bearing journals and the

bearings to 0.8596 to 0.8593-inch diameter.

sleeve bearings with engine oil. Install the cap on its

c. If the pistons and pins are not being replaced,

connecting rod (21, fig. 9-20) and crank pin bearing

check the clearance between the piston pins and the

journal; secure with the two bolts (18) and nuts (20).

sleeve bearings. Clearance must be between 0.0000

Tighten the nuts to 35 to 40 ft/lbs torque. Install the

and 0.005 inch. If clearance is not within this tolerance,

cotter pins (19).

press new sleeve bearings into the connecting rods and

Secure the remaining connecting rods to the

ream and hone to provide the proper clearance. After

crank pin bearing journals.

honing, 75 percent of the sleeve bearing surface must

contact the piston pin.

d. When pins, bushings, and pistons of the proper

size have been found, assemble the pistons to the

connecting rods as follows:

(1) Heat the pistons and connecting rods in an

oven or in water to a minimum of 160 F.

9-19