Visually inspect each bearing shell for defects and signs of uneven wear. Interpret bearing shell appearance as
Bearing shells that have been operating at the correct clearance and with adequate lubrication will have a
dull gray color. Bearing shells having a black surface, or showing varnish build-up, have been running at
excessive clearance and shall be replaced.
Bearing shells that show bright shiny spots or areas have been running at insufficient clearance and shall
be replaced. If bright areas appear along one edge of the bearing shell misalignment exists. Check the
connecting rod for alignment in accordance with paragraph 9-20.
Bearing shells that are flaked, scored, galled, or show visible embedded dirt particles shall be replaced.
Using a micrometer having a ball anvil, measure each bearing shell. Minimum thickness for connecting rod
bearing shells shall be in accordance with Table 1-4. If either shell of a bearing set is under the minimum
thickness, replace both shells.
Inspect the crankshaft journal as follows: (a) Visually inspect the journal for cracks, nicks, pitting, scoring, or
grooving. Replace the crankshaft in accordance with paragraph 9-27 if cracked. Rebuild the crankshaft in
accordance with paragraph 9-28 if surface defects are over 0.003 inch (0.08 mm) deep.
Using an outside micrometer, check the journal for wear, out-of-round, and taper. Rebuild the crankshaft
in accordance with paragraph 9-28 if is worn more than the limits specified in Table 1-4, out-of-round more
than 0 .002 inch (0.005 mm), or tapered more than 0.0005 inch (0.013 mm) over the full length of the
Visually inspect the thrust surfaces for cracks, nicks, pitting, scoring, or grooving. Rebuild the crankshaft in
accordance with paragraph 9-28 if surface defects are over 0.003 inch (0.008 mm) deep.
During bearing shell Installation procedures, be sure all parts are kept dean and free of dirt or
other foreign materials Be especially careful when Installing the bearing shells in the
connecting rod and cap. Even a small amount of foreign matter trapped between the bearing
shells and the rod or cap, will decrease bearing shell-to-journal clearance and result in
premature wear or burned bearIng shells.
Bearing shells must be replaced in sets only.
Remove all traces of oil and foreign material from the mating and bearing surfaces of the connecting rod (4) and
Install serviceable or replacement bearing shells (11) in the connecting rod (4) and cap (3). Be sure the bearing
shells are firmly seated in the rod and cap.
(3) Pull the connecting rod into position on the journal, and remove the guide pins 3375098 from the connecting rod.
Plastigage is available in three clearance ranges: Type PG-1 (green) for a clearance range of
0.001 to 0.003 inch (0.025 to 0.076 mm); Type PR-1 (red) for a clearance range of 0.002 to 0.006
inch (0.051 to 0.152 mm); Type PB1 (blue) for a clearance range of 0.004 to 0.009 inch (0.102 to
0.229 mm). Select the range needed for the clearance being checked in accordance with Table
(4) Place a strip of Plastgage across the full width of the bearing shell in the rod cap (A, Figure 9-32).
Before installing the connecting rod bolts (1, Figure 9-24) and washers (2), coat the bolt
threads, under side of bolt heads, and washers with dean lubricating oil MIL-L-2104.
Being careful not to dislodge the Plastigage, install the bearing cap (3, Figure 9-24) on the connecting rod (4) and
retain with washers (2) and bolts (1). Tighten the bolts in accordance with Table 1-3.