inspection equipment is available, use it to check the
crankshaft for hidden flaws.
Replace a damaged
Upper main bearing shells can be removed
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.
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.
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
with the timing marks on the camshaft gear.
See paragraph 9-37.
Install the lower half of the bearing shells in the
Dry cleaning solvent, P-D-680, used to clean
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:
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
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