Service manual

Measuring Crankshaft Bearing Clearances
Notice: SIO-ID = 5016 Do not shim, scrape, or file
bearing inserts. Do not touch the bearing surface of the
insert with bare fingers. Skin oil and acids will etch
the bearing surface.
• The crankshaft bearings are precision insert type
and do not use shims for adjustment. If the
clearances are excessive, then new upper and
lower crankshaft bearings will be required.
The service crankshaft bearings are available in
the standard size and an undersize.
• The selective fitting of the crankshaft bearings are
necessary in production in order to obtain close
tolerances. For this reason, in one journal
bore you may use one-half of a standard
crankshaft bearing with one-half of an undersize
crankshaft bearing.
• In order to determine the correct replacement
bearing size, the bearing clearance must be
measured accurately. When checking main
bearing clearances, either the micrometer or
plastic gage method may be used. The micrometer
method gives more reliable results and is
preferred. When checking connecting rod bearing
clearances, the plastic gage method will result
in unreliable measurements. The use of
J 43690
is preferred.
• If the crankshaft bearing clearance is within
specifications, the crankshaft bearing is
satisfactory. If the clearance is not within
specifications, replace the crankshaft bearing.
Always replace both the upper and lower
crankshaft bearings as a unit.
• A standard, or undersize crankshaft bearing
combination, may result in the proper clearance. If
the proper crankshaft bearing clearance cannot
be achieved using the standard or the undersize
crankshaft bearings, it may be necessary to
repair or replace the crankshaft.
Measuring Crankshaft Bearing Clearances –
Micrometer Method
1. Measure the crankshaft journal diameter with a
micrometer in several places, approximately
90 degrees apart. Average the measurements.
2. Determine the taper and out-of-round of the
journal. Refer to
Engine Mechanical Specifications
(5.0 L)
or Engine Mechanical Specifications
(5.7 L)
.
188015
188015
Engine Engine Mechanical - 5.0L and 5.7L 6-55
2002 - Unit Repair (May 25, 2001)