249
POWERHEAD
INSPECTION
10
Cylinder Bore
Use Cylinder Bore Gauge, P/N 771310, to inspect
each cylinder bore for an out-of-round, oversize,
or tapered condition. Be sure the gauge is per-
fectly square in the bore when measuring.
Measure each cylinder in at least two areas. Each
area should be measured twice. The difference
between the two measurements in each area is
the cylinder out-of-round dimension.
• The cylinder must not be out-of-round by more
than 0.004 in. (0.10 mm).
The dimensional difference between the two
areas is cylinder taper.
• The cylinder taper must not exceed 0.002 in.
(0.05 mm).
The difference between the measurements and
standard bore is cylinder oversize. For dimen-
sions, refer to TECHNICAL DATA on p. 18.
• The cylinder must not be oversized by more
than 0.004 in. (0.10 mm).
IMPORTANT: If any cylinder is outside these
tolerances, it must be bored oversize. It is permis-
sible to have one or more oversize pistons in an
engine.
Pistons
Visually inspect pistons for signs of abnormal
wear, scuffing, cracks, or burning.
Piston Rings
For new ring sets, place each ring separately in its
respective bore. Use a piston to square the ring in
the cylinder. Use a feeler gauge to measure the
ring end gap.
IMPORTANT: Ring end gap increases approxi-
mately 0.003 in. (0.08 mm) for each 0.001 in.
(0.025 mm) increase in cylinder bore diameter.
DO NOT exceed cylinder oversize dimension.
Use a machinist’s straightedge to check for proper
ring clearance. Position piston rings on piston.
Push rings into groove and hold straightedge
against the side of the piston. Rings must be even
Measure as shown 46528
1. Cylinder taper DR3482
1
002143
Ring End Gap Specification
Standard or
Oversize rings
0.011 to 0.023 in.
(0.28 to 0.58 mm)
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