Main Bearings and Crankshaft - TM-5-4320-234-340082

TM 5-4320-234-34

bearing and journal, and install the bearing cap. Tighten

ring exceeds 0.017 inch (0.0425 cm), the cylinder is

the connecting rod cap bolts to 40 to 45 footpounds

worn oversize and the cylinder block must be replaced.

(5.532 to 6.223 kgm) torque. Rotate the crankshaft to

(6) Install the oil ring in the bottom ring

determine the amount of drag. If clearance is within

groove of each piston as follows: (a) Place stainless

tolerance, you will feel a definite drag. Disassemble the

steel expander spacer in groove with ends butted.

rod cap and remove the shim stock. If clearance is not

(b) Install steel segment on top side of

within tolerance, replace the connecting rod bearings

expander spacer with gap of segment approximately 90

and recheck the clearance. If clearance is still not within

beyond gap of stainless steel expander spacer, making

tolerance, replace the crankshaft.

certain that the expander spacer ends are still in a

(12) Lubricate the crank pin bearing journals

butted position.

and the sleeve bearings with engine oil. Install the cap

(13, fig. 4-13) onto its connecting rod (20) and crank pin

of the

expander

spacer

with

segment

gap

bearing journal; secure with the two bolts (12) and nuts

approximately 90 from the expander gap in opposite

(11). Tighten the nuts to 40 to 45 footpounds (5.532 to

direction from which the top segment has been installed.

6.223 kgm) torque. Install the cotter pins (10).

(d) Recheck assembly. Rings should be

(13) Secure the remaining connecting rods to

free to move in the groove; however, you will notice a

the crank pin bearing journals.

slight drag because of the side sealing action of the ring

(14) Install the engine oil pan (para 4-5c) and

assembly. Be sure expander spacer ends remain

oil pump (para 4-6c).

butted.

(15) Install the cylinder head (para 4-3r).

(7) Install the remaining piston rings on the

piston with a standard ring expander tool.

(8) Assemble

the

remaining

pistons,

4-10. Main Bearings and Crankshaft

connecting rods, and piston rings.

(9) Install the assembled pistons and

Removal and Disassembly.

With the engine

connecting rods in the same cylinders from which they

mounted on an engine overhaul stand, proceed as

were originally removed. Use a ring compressor to

follows: (1) Remove the cylinder head (para 4-3a).

compress the piston rings. Lubricate the pistons and

(2) Remove the oil pan (para 4-5a) and oil

cylinder walls with engine oil before installing the

pump (para 4-6a).

pistons. Wrap the bottom ends of the connecting rods

(3) Remove the gear cover (para 4-7a).

with cloths to prevent damage to the cylinder walls

(4) Remove the flywheel and flywheel

during installation.

housing (para 4-8a).

(10) Check the crank pin bearing journal-to

(5) Remove the pistons and connecting rods

connecting rod bearing clearance with plastigage. Lay a

(para 4-9a).

piece of plastigage material on the crankshaft journal

(6) Remove the bolts (24 and 28, fig. 4-13)

and install the connecting rod bearing cap. Torque the

that secure the main bearing caps (25, 29, 32, and 34)

nuts to 40 to 45 foot-pounds (5.532 to 6.223 kgm).

to the cylinder block. Loosen the bearing caps by

Remove the bearing cap and compare the width of the

tapping them with a plastic hammer. Remove the

flattened plastigage material with the scale markings on

bearing caps and lower bearings (27, 30, 33, and 35).

the plastigage package to determine the clearance. The

bearing-to-journal clearance shall be 0.006 to 0.0022

NOTE

inch (0.0015 to 0.0055 cm). If clearance is beyond

Upper main bearing shells can be removed without

removing the crankshaft. To remove the upper shell,

these limits, replace the bearing and/or the crankshaft

remove the main bearing cap at the defective bearing and

as required.

remove the lower bearing shell. Insert a pin with an

(11) As an alternate method of checking crank

angular head into the oil hole of the crankshaft as shown

bearing

journal-to-connecting

rod

bearing

in figure 4-15. Rotate the crankshaft and roll the bearing

clearance, install a 1/2 inch (1.250 cm) piece of

shell from the cylinder block.

0.0022inch (0.0055 cm) thick feeler stock between the

4-16