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E. Measure the diameter of the alignment dowel (Dimension A) shown in Figure 32 and
determine if the measurement conforms to the values for the different alignment dowel part
numbers in the latest revision of Service Bulletin No. SB-475 for additional details.
F. If the alignment dowel is out of tolerance or out of round, replace the dowel with a new one
per the "Alignment Dowel Replacement" procedure in this chapter.
8. Crankshaft Bearing Surface Inspection
Examine all bearing surfaces for scoring, galling, and wear.
A.
Refer to the latest revision of Service Table of Limits - SSP-1776 to identify the nominal
B.
manufactured specifications of the bearing journals. Undersize crankshaft bearing journals in
Table 1 are identified by a code symbol stamped on the front of the flange as a suffix to the
part number.
Journals
Main Bearing Journals
Using a micrometer, measure and record the dimensions.
C.
If the actual undersize is between the service limit (0.0015 in. and 0.003 in.), complete the
D.
following:
(1) Polish to 0.003 in. (0.076 mm) undersize.
(2) Fit with 0.003 in. (0.076 mm) bearing insert.
(3) Repeat for all bearings.
CAUTION
NOTICE: Polishing undersize is preferable to grinding undersize because shafts that are
polished do not require re-nitriding.
If one bearing journal is polished to 0.003 in. or 0.006 in. undersize, all
corresponding journals must be polished to the same size.
If, after the bearing journal is polished to 0.003 in. (0.076 mm), the bearing journal requires
E.
more polishing complete the following:
(1) Polish to 0.006 in. (0.152 mm) undersize.
(2) Fit with 0.006 in. (0.152 mm) bearing insert.
(3) Repeat for all like bearings.
If the actual undersize is greater than 0.006 in. (0.152 mm), replace the crankshaft.
F.
72-20
Page 150
Table 1
Crankshaft Undersize Codes
0.003 in. (0.076 mm)
M03M
DURING POLISHING, DO NOT ALLOW THE LATHE SPEED TO
EXCEED 150 RPM.
IO-390-D Series Engine Maintenance Manual
IO-390-D Series Engine Maintenance Manual
0.006 in. (0.152 mm)
© 2020 Avco Corporation. All Rights Reserved
M06M
March 2020
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