4. Inspect the upper and lower bearing
shells as outlined under "Inspection" on
page 11B-82.
5. Install the bearing shells and bearing
caps before another connecting rod bear-
ing is removed.
Inspection
Bearing failures may result from deteri-
(acid formation) or contam-
orations
ination
of
the
oil
or
loss
of
oil.
An
addition
In
the
thickness
to
analysis of the lubricating oil may be re-
measurement,
check the clearance be-
quired to determine if corrosive acid and
tween the connecting rod bearing shells
sulphur are present which cause acid
and the crankshaft journal. This clear-
Bearing
etching, f l a k i n g a n d p i t t i n g .
ance may be checked by means of a soft
s e i z u r e may be due to low oil or no oil.
plastic measuring strip which is squeezed
between the journal and bearing (refer
After removal, clean the bearings and
to "Shop Note - Troubleshooting" on
pitting,
for
scoring,
them
inspect
page 11B-121). The maximum connecting
flaking, chipping, cracking, loss of bab-
rod bearing-to-journal clearance with
If any of
bitt or signs of overheating.
used parts is 0.006".
these defects are present, the bearings
However, babbitt
must be discarded.
Before installing the bearings, inspect
may develop minute
bearings
plated
the crankshaft journals.
cracks or small isolated cavities on the
bearing surface during engine operation.
Do not replace one connecting rod bear-
These are characteristic of and are NOT
ing shell alone.
If one bearing shell re-
detrimental to this type of bearing. The
install both new
quires
replacement,
bearings s h o u l d n o t b e r e p l a c e d f o r
upper and lower bearing shells. Also, if
the
these minor surface imperfections.
a new or reground crankshaft is to be
upper bearing shells, which carry the
used, install all new bearing shells.
load, will normally show signs of distress
before the lower bearing shells do.
Bearing shells are available in 0.010",
0.020" and 0.030" undersize for service
Inspect the backs of the bearing shells
with reground crankshafts.
To deter-
for bright spots which indicate they have
mine the size bearings required, refer to
been shifting in their supports. If such
"Crankshaft Grinding" on page 11B-49.
spots a r e p r e s e n t , d i s c a r d t h e b e a r i n g
Bearings which are 0.,002" undersize are
Also inspect the connecting rod
shells.
available to compensate for slight journal
burrs,
foreign
for
bore
bearing
wear where it is unnecessary to regrind
particles, etc..
the crankshaft.
Measure the thickness of the bearing
NOTE
shells, using a micrometer and attach-
ment J 4757, as described under "In-
Bearing shells are NOT reworkable
spection" on page 11B-57. The minimum
from one undersize to another un-
thickness of a worn standard connecting
der any circumstances.
rod bearing shell should not be less than
0.1530" and, if either bearing shell is
thinner than this dimension, replace both
bearing shells. A new standard bearing
I n s t a l l Connecting Rod Bearing Shells
shell has a thickness of 0.1548" to
The dimensions of undersize
0.1553".
With the crankshaft and the piston and
bearings are shown in the following
connecting rod assembly in place, install
table.
the connecting rod bearings as follows:
1. Rotate the crankshaft until the con-
necting rod journal is at the bottom of its
