TM 10-4320-307-24
4-17
CRANKSHAFTASSEMBLY REPLACE/REPAIR (CONT)
7.
Measure crankshaft main bearing journals as follows:
a.
Using micrometer, measure diameter of each
crankshaft main bearing journal (1) at points A
and B, along axes X and Y.
b.
The maximum acceptable diameter for journal
is 4.4975 inches (114.237 mm). However, if
journals are evenly worn, not out of round. and
crank pin diameters are within specified limits,
only main bearing bushings need be replaced.
Crankshaft Journal Diameters - Inch (mm)
Journal
Minimum
Maximum
Worn Limit
Main
4.4985
4.500
4.4975
Bearing
(114.262)
(114.30)
(114.237)
c.
If measurements at points A and B indicate more than 0 005 inch (0.013 mm) taper per length of journal, and/or
one set is outside specified limits, journal is worn In a conical shape and crankshaft must be replaced.
d.
If measurements along X and Y axes differ and, or one set is outside specified limits. journal is worn into an oval
shape.
NOTE
For both above out-of-round conditions, also check connecting rods. pistons. cylinders,
and main bearing bushings for unusual wear.
e.
Measure width of crankshaft journals.
f.
Measure fillet radius at each crankshaft main journal using fillet ball gauge set (3). Fillet radius should measure
from 0.1693 to 0.1772 inch (4.30 to 4.50 mm). If any fillet measurement is out of limits. replace crankshaft. Fillet
must blend smoothly into journal check. and must be free from scratches. Polish and smooth any slight
imperfections with crocus cloth wet with lubricating oil.
8.
Check crankshaft main bearing clearances as follows:
a
Assemble upper bearing shell, lower bearing shell and bearing cap to cylinder head, using hexagon screws and
washers. Torque screws in accordance with installation instructions.
b.
Measure inside diameter of bearing shells.
c.
Subtract journal outside diameter (previously measured) from bearing shell inside diameter to obtain clearance
between shell and journal.
Bearing Clearance - Inch (mm)
Bearing
New Dimension
Journal
Minimum
Maximum
Worn Limit
Main
0.0015
0.0050
0.0070
Bearing
(0.038)
(0.127)
(0.178)
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