TM 5-3895-359-14&P
Bearing shells are available in .010", .020" and .030 "
After removal, clean the bearings and inspect them for
scoring, pitting, flaking, chipping, cracking, loss of
undersize for service with reground crankshafts. To
determine the size bearings required, refer to
babbitt or signs of overheating. If any of these defects
are present, the bearings must be discarded. However,
Crankshaft Grinding on Page 10-2-52. Bearings which
are .002" undersize are available to compensate for
babbitt plated bearings may develop minute cracks or
slight journal wear where it is unnecessary to regrind the
small isolated cavities on the bearing surface during
crankshaft.
engine operation. These are characteristics of and are
NOT detrimental to this type of bearing. The bearings
should not be replaced for these minor surface
NOTE: Bearing shells are NOT reworkable
imperfections. The upper bearing shells, which carry
from one undersize to another under any
the load, will normally show signs of distress before the
circumstances.
lower bearing shells do.
Install Connecting Rod Bearing Shells
Inspect the backs of the bearing shells for bright spots
With the crankshaft and the piston and connecting rod
which indicate they have been shifting in their supports.
assembly in place, install the connecting rod bearings as
If such spots are present, discard the bearing shells.
follows:
Also inspect the connecting rod bearing bore for burrs,
foreign particles, etc.
1. Rotate the crankshaft until the connecting rod journal
is at the bottom of its travel, then wipe the journal clean
Measure the thickness of the bearing shells, using a
and lubricate it with clean engine oil.
micrometer and ball attachment J 4757, as described
2. Install the upper bearing shell -the one with the short
under Inspection on Page 10-2-60. The minimum
groove and oil hole at each parting line -in the
thickness of a worn standard connecting rod bearing
connecting rod. Be sure the tang on the bearing shell
shell should not be less than .1530" and, if either
fits in the groove in the connecting rod.
bearing shell is thinner than this dimension, replace both
3. Pull the piston and rod assembly down until the
bearing shells. A new standard bearing shell has a
upper rod bearing seats firmly on the crankshaft journal.
thickness of .1548" to .1553". Refer to Table 1.
4. Note the numbers stamped on the connecting rod
Bearing
'New Bearing
Minimum Worn
and the bearing cap and install the lower bearing shell -
Size
Thickness
Thickness
the one with the continuous oil groove -in the bearing
cap, with the tang on the bearing shell in the groove in
the bearing cap.
Standard
.1548"/. 1553"
.1530"
5.
Install the bearing and cap and tighten the
connecting rod bolt nuts to 60-70 lb-ft (81-95 N )
.002" Undersize
.1558".1563"
/
.1540"
m
torque (lubrite nut) or 65-75 lb-ft (88-102 N ) torque
m
.010" Undersize
.1598"/.1603"
.1580"
(castellated nut).
.020" Undersize
.1648"/.1653"
.1630"
NOTE: Be sure the connecting rod bolt has not
turned in the connecting rod before torque is
.030" Undersize
.1698"/.1703"
.1 680"
applied to the nut.
*Thickness 90from parting line of bearing.
TABLE 1
6. Install the lubricating oil pump and the oil inlet and
In addition to the thickness measurement, check the
outlet pipes.
clearance between the connecting rod bearing shells
and the crankshaft journal. This clearance may be
NOTE: If shims were used between the oil
checked by means of a soft plastic measuring strip
pump body and the main bearing caps, install
which is squeezed between the journal and the bearing
the shims in exactly the same location from
(refer to Shop Notes on Page 10-2-131.) The maximum
which they were removed.
connecting rod bearing-to-journal clearance with used
parts is .006" .
7. Install the oil pan, using a new gasket.
8. Refer to the Lubricating Oil Specifications on Page
Before installing the bearings, inspect the crankshaft
journals (refer to Inspection on Page 10-2-49).
dipstick.
If new bearings were installed, operate the engine on the
Do not replace one connecting rod bearing shell alone.
run-in schedule as outlined on Page 10-9-2.
If one bearing shell requires replacement, install both
new upper and lower bearing shells. Also, if a new or
reground crankshaft is to be used, install all new bearing
shells.
10-2-91
