Replacement bearings are available in standard size and undersize (for reground
crankshafts). Connecting rod-to-crankshaft bearing clearance is checked using
Plastigage® at either the top or the bottom of each crank journal.
The Plastigage® has a range of 0.001–0.003 inch (0.0254–0.0762mm).
- Remove the rod cap with the bearing shell. Completely clean the bearing
shell and the crank journal, blow any oil from the oil hole in the crankshaft;
place the Plastigage® lengthwise along the bottom center of the
lower bearing shell, then install the cap with the shell and tighten the bolt
or nuts to specification. DO NOT turn the crankshaft with the Plastigage® on
the bearing.
- Remove the bearing cap with the shell. The flattened Plastigage® will
be found sticking to either the bearing shell or the crank journal. DO NOT
remove it yet.
- Use the scale printed on the Plastigage® envelope to measure the
flattened material at its widest point. The number within the scale which
most closely corresponds to the width of the Plastigage® indicates
the bearing clearance in thousandths of an inch and millimeters.
- Check the specifications chart in this section for the desired clearance.
It is advisable to install a new bearing if the clearance exceeds specification;
however, if the bearing is in good condition and is not being checked because
of bearing noise, bearing replacement is not necessary.
- If you are installing new bearings, try a standard size, then each undersize
in order until one is found that is within the specified limits when checked
for clearance with Plastigage® ; each undersize shell has its size
stamped on it.
- When the proper size shell is found, clean off the Plastigage® ,
oil the bearing thoroughly, reinstall the cap with its shell and tighten the
rod bolt nuts to specifications.
NOTE: With the proper bearing selected and the nuts torqued,
it should be possible to move the connecting rod back and forth freely on
the crank journal as allowed by the specified connecting rod end clearance.
If the rod cannot be moved, either the rod bearing is too far undersize
or the rod is misaligned.
