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231 V6 ENGINE V.I. CODE C
6A3-13
Fig. 6A3-26 Measuring Gear Pocket For Wear
surface of rod or cap.
If a rod bearing becomes noisy or is worn so that
clearance on the crankpin is excessive, a new bearing of
proper size must be selected and installed since no provision
is made for adjustment. Under no circumstances
should the connecting rod or cap be filed to adjust
the bearing clearance.
INSPECTION OF CONNECTING ROD
BEARINGS AND CRANKPIN JOURNALS
After removal of engine oil pan, disconnect two
connecting rods at a time from crankshaft and inspect the
bearings and crankpin journals. While turning crankshaft it
is necessary to temporarily reconnect the rods to crankpin to
avoid possibility of damaging the journals through contact
with loose rods. Do not interchange rod caps with rods.
If connecting rod bearings are scored or show flaking,
they should be replaced. If bearings are in good physical
condition check for proper clearance on crankpin.
If crankpin journals are scored or ridged the crankshaft
must be replaced, or reground for undersize bearings, to
insure satisfactory life of connecting rod bearings. Slight
roughness may be polished out with fine grit polishing cloth
thoroughly wetted with engine oil. Burrs may be honed off
with a fine oil stone.
Use an outside micrometer to check crankpins for out-
of-round. If crankpins are more than .0015" out-of-round,
satisfactory life of new bearings cannot be expected.
Checking Clearance and Selecting Replacement
Bearings
Service bearings are furnished in standard size and
several undersizes (including undersizes for re-ground
crankpins).
The clearance of connecting rod (and crankshaft)
bearings may be checked by use of Plastic-Type Gage which
has a range of .001" to .003".
1. Remove connecting rod cap with bearing shell. Wipe
oil from bearing and crankpin journal, also blow oil out of
hole in crankshaft. Plastic-type gage is soluble in oil.
2. Place a piece of plastic-type gage lengthwise along the
bottom center of the lower bearing shell (Fig. 6A3-27, View
A), then install cap with shell and torque bolt nuts to
specifications.
L
481 6
Fig. 6A3-27 Checking Bearing Clearance With Plastic-
Type Gage
Conical boss on web of rod must be toward rear of engine
on all rods in left bank and toward front of engine in right
bank. Cap installation can be only one direction since it is
dictated by bolt centerline onset.
3. DO NOT TURN CRANKSHAFT with plastic-
type gage in bearing.
4. Remove bearing cap with bearing shell, the flattened
plastic-type gage will be found adhering to either the bearing
shell or the crankpin. Do not remove it.
5. Using the scale printed on the plastic-type gage
envelope, measure the flattened plastic-type gage at its widest
point. The number within the graduation which most closely
corresponds to the width of plastic-type gage indicates the
bearing clearance in thousandths of an inch. See Fig. 6A3-27,
View B.
6. The desired clearance with a new bearing is .0005"
to .0026". If bearing has been in service it is advisable to
install a new bearing if the clearance exceeds .003"; however,
if bearing is in good condition and is not being checked
because of bearing noise, it is not necessary to replace the
bearing.
7. If a new bearing is being selected, try a standard size,
then each undersize bearing in turn until one is found that
is within the specified limits when checked for clearance with
plastic-type gage. Each undersize bearing shell has a number
stamped on the outer surface to indicate amount of undersize.
See Fig. 6A3-28.
8. After the proper size bearing has been selected, clean
off
the plastic-type gage, oil the bearing thoroughly, reinstall
cap with bearing shell and torque bolt nuts to specifications.
See Step 2.
9. With selected bearing installed and bolts tightened, it
should be possible to move connecting rod freely back and
forth on crankpin as allowed by end clearance. If rod cannot
be moved, either the bearing is too much undersize or a
misaligned rod is indicated.
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