TM 9-2320-289-34
3-14.
CHECKING MAIN BEARING CLEARANCE (Con’t).
CAUTION
Ensure that main bearing caps (1) are fully seated before installing bolts (2
and 3). Failure to follow this caution may result in damage to main bearing
caps.
l
l
NOTE
Inner bolts (3) are longer than outer bolts (2).
Ensure that lubricating oil is applied to bolt (2 and 3) threads before
installation,
3.
Using soft-faced hammer, tap main bearing #3 cap (1) into place and install 2 inner bolts (3)
and 2 outer bolts (2). Tighten all bolts to 40 Ib. -ft. (54 N-m). Evenly tighten inner bolts again to
110 Ib.-ft. (149 N.m). Evenly tighten outer bolts again to 100 Ib.-ft. (136 N.m).
NOTE
Scale on envelope (7) of gaging plastic (6) should be used to measure
clearance.
DO NOT rotate crankshaft (5) while gaging plastic (6) is between main
bearing (4) and crankshaft.
This will result in an inaccurate
measurement.
4.
Remove 2 inner bolts (3), 2 outer
bolts (2), and main bearing #3 cap
(1). Measure flattened gaging plastic
(8) at widest point to determine main
bearing clearance. Preferred main
bearing
clearance
is 0.0018 in.
(0.0457 mm) for main bearings #1-4
and 0.0033 (0.0838 mm) for main
bearing #5. Clearance should be no
more than 0.005 in. (0.127 mm).
5.
Measure flattened gaging plastic (8)
at
each
end
and
middle,
and
compare
readings.
Maximum
difference between ends and middle
(taper)
should
be
0.001 in.
(0.025 mm). If there is taper,
measure
crankshaft (5) journal.
Replace
crankshaft if
there
is
excessive taper. (See paragraph
3-1 5) Discard gaging plastic.
6.
If measurements in steps 4 and 5 are not correct, replace main bearing (4) (see
paragraph 3-1 5) and repeat steps 2-5. If still not within specifications, use undersized main
bearing. If smallest undersized bearing has been used, replace crankshaft (5). (See
paragraph 3-1 5)
TA50656
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