1.6.2 Connecting Rod Bearings
DETROIT DIESEL 53
Bearing
Bearing
Minimum
Size
Thickness
Thickness
In Line Engines
Standard
. 1245"/. 1250"
. 1230"
.002" Undersize
. 1255"/.1260"
. 1240"
.010" Undersize
. 1295"/.1300"
. 1280"
.020" Undersize
. 1345"/.1350"
. 1330"
.030" Undersize
. 1395"/.1400"
. 1380".
V - Type Engine
Standard
. 1247"/.1252"
. 1230"
.002" Undersize
. 1257"/.1262"
. 1240"
.010" Undersize
. 1297"/.1302"
. 1280"
.020" Undersize
. 1347"/.1352"
. 1330"
.030" Undersize
. 1397"/.1402"
. 1380"
TABLE 1
carry the load, will
normally show signs of distress before the lower bearing shells do.
Inspect the backs of the bearing shells for bright spots which indicate they have been shifting in their supports. If such
spots are present, discard the bearing shells. Also inspect the connecting rod bearing bore for burrs, foreign particles,
etc.
Measure the thickness of the bearing shells, using a micrometer and ball attachment J 4757, as described under
Inspection in Section 1.3.4. The minimum thickness of a worn standard connecting rod bearing shell should not be less
than .1230" and, if either bearing shell is thinner than this dimension, replace both bearing shells. A new standard
bearing shell has a thickness of .1245"to .1250"(in-line engine), Refer to Table 1.
In addition to the thickness measurement, check the clearance between the connecting rod bearing shells and the
crankshaft journal. This clearance may be checked by means of a soft plastic measuring strip which is squeezed
between the journal and the bearing (refer to Shop Notes in Section 1.0). The maximum connecting rod bearing-to-
journal clearance with used parts in .006".
Before installing the bearings, inspect the crankshaft journals (refer to Inspection in Section 1.3). Do not replace one
connecting rod bearing shell alone. 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.
Bearing shells are available in .010", .020" and .030" undersize for service with reground crankshafts. To determine the
size bearings required, refer to Crankshaft Grinding in Section 1.3. Bearings which are .002" undersize are available to
compensate for slight journal wear where it is unnecessary to regrind the crankshaft.
NOTE: Bearing shells are NOT reworkable from one undersize to another under
any circumstances.
Install Connecting Rod Bearing Shells
With the crankshaft and the piston and connecting rod in place, install the connecting rod bearings as follows:
1. Rotate the crankshaft until the connecting rod journal is at the bottom of its travel, then wipe the journal clean and
lubricate it with clean engine oil.
2. Install the upper bearing shell -- the one with the short groove and oil hole at each parting line -- in the connecting
rod. Be sure the tang on the bearing shell fits in the groove in the connecting rod.
3. Pull the piston and rod assembly down until the upper rod bearing seats firmly on the crankshaft journal.
4. Note the numbers stamped on the connecting rod and the bearing cap and install the lower bearing shell -- 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.
5. Install the bearing and cap and tighten the nuts on the 3/8"-24 bolts (In-line engines) to 40-45 lb-ft torque.
6. Install the lubricating oil pump inlet tube assembly. Replace the inlet tube seal ring or elbow gasket if hardened or
broken.
7. Install the oil pan, using a new gasket.
8. Refer to the Lubricating Oil Specifications in Section 13.3 and fill the crankcase to the proper level on the dipstick.
9. If new bearings were installed, operate the engine on the run-in schedule as outlined in Section 13.2.1.
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