DETROIT DIESEL 53
1.6.2 Connecting Rod Bearings
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
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.
carry the load, will normally show signs of distress
2. Install the upper bearing shell -- the one with the
before the lower bearing shells do.
short groove and oil hole at each parting line -- in the
connecting rod. Be sure the tang on the bearing shell
Inspect the backs of the bearing shells for bright spots
fits in the groove in the connecting rod.
which indicate they have been shifting in their
supports. If such spots are present, discard the bearing
3. Pull the piston and rod assembly down until the
shells. Also inspect the connecting rod bearing bore
upper rod bearing seats firmly on the crankshaft
for burrs, foreign particles, etc.
Measure the thickness of the bearing shells, using a
4. Note the numbers stamped on the connecting rod
micrometer and ball attachment J 4757, as described
and the bearing cap and install the lower bearing shell
under Inspection in Section 1.3.4. The minimum
-- the one with the continuous oil groove -- in the
thickness of a worn standard connecting rod bearing
bearing cap, with the tang on the bearing shell in the
shell should not be less than .1230" and, if either
groove in the bearing cap.
bearing shell is thinner than this dimension, replace
both bearing shells. A new standard bearing shell has
5. Install the bearing and cap and tighten the nuts on
a thickness of .1245" to .1250" (in-line engine).
engines) to 40-45
the 3/8" -24 bolts (In-line
Refer to Table 1.
In addition to the thickness measurement, check the
clearance between the connecting rod bearing shells
6. Install the lubricating oil pump inlet tube assembly.
and the crankshaft journal. This clearance may be
Replace the inlet tube seal ring or elbow gasket if
checked by means of a soft plastic measuring strip
hardened or broken.
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).
7. Install the oil pan, using a new gasket.
Do not replace one connecting rod bearing shell alone.
8. Refer to the Lubricating Oil Specifications in
If one bearing shell requires replacement, install both
Section 13.3 and fill the crankcase to the proper level
new upper and lower bearing shells. Also, if a new or
on the dipstick.
reground crankshaft is to be used, install all new
9. If new bearings were installed, operate the engine
on the run-in schedule as outlined in Section 13.2.1.