3-68
DE351
24. Making sure pistons are clean and ring lands are
free of carbon deposits, measure ring to ring-land
clearance using new piston rings. If ring to ring-
land clearance is excessive, new pistons must be
installed.
DE367
25. Using a suitable outside micrometer, measure pis-
ton skirt diameter at a distance of 9 mm (0.350 in.)
from the bottom of the skirt and 90° from the pis-
ton pin axis. Pistons and cylinder measurements
must be within specifications as listed in the fol-
lowing chart. Class markings are stamped on the
cylinder deck.
DE354
DE356B
NOTE: Replacement pistons are only supplied as
class A. Class B and C are reserved for production
engines. Replacement pistons are available over-
sized by 0.50 mm (0.020 in.) and 1.00 mm (0.039 in.)
and are supplied with piston rings.
NOTE: The engine block must be bored in order
to install oversized pistons.
26. Thoroughly clean all components after machining
to insure no filings or metal chips are present.
Blow out all oil galleys with compressed air.
Installing
1. Mount the engine block on a suitable engine stand;
then install the upper main bearing inserts into the
main bearing saddles making sure the oil holes in
the inserts are aligned with the oil galleys in the
saddles and the locating tabs are oriented in the
reliefs.
Class
Cylinder
Diameter
Piston Diameter
Clearance
A
74.990-75.000
(2.9523-2.9527 in.)
74.930-74.940 mm
(2.9499-2.9503 in.)
0.050-0.070 mm
(0.002-0.003 in.)
B
75.000-75.010 mm
(2.9527-2.9531 in.)
74.940-74.950 mm
(2.9503-2.9508 in.)
0.050-0.070 mm
(0.002-0.003 in.)
C
75.010-75.020 mm
(2.9531-2.9535 in.)
74.950-74.960 mm
(2.9508-2.9512 in.)
0.050-0.070 mm
(0.002-0.003 in.)
CAUTION
Do not attempt to use standard rings on oversized
pistons or oversized rings on standard pistons.
Severe engine damage will occur.
! WARNING
Always wear safety glasses when using compressed
air.
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