User Manual

200 BENCH PROCEDURES
Page 5-15
Inspection
Inspect piston ring grooves, lands, piston skirt
and combustion bowl for wear, scuffing, cracks or
blow-by. Pistons are NOT repairable. Discard
piston if it is damaged.
Do not stamp or engrave on TOP of piston. Doing
so will reduce piston life.
To ensure that pistons are reinstalled in the same
cylinders as removed, tag the piston with the
corresponding cylinder number.
[212 NV] PISTON RINGS
Before installing piston rings, check keystone ring
groove wear and ring end gap.
1. Place a piston ring in the piston sleeve.
Push it down into the sleeve with an inverted
piston to ensure that it is positioned squarely
in sleeve.
2. Using thickness gauges, check ring end
gap. Refer to the Fits and Limits chart in the
SPECIFICATIONS section for end gap
specifications. All rings to be used should be
checked in this manner.
Do not file or grind chrome-plated piston rings.
This may cause chrome to flake, resulting in ring
failure.
Keystone Ring Groove Check
Refer to Figure 5-12.
Keystone piston-ring groove gauge J 29510
consists of two 0.120-inch (3.048 mm) diameter
pins (1) connected at ends by two springs (2).
Figure 5-12 — Ring Groove Gauge
1. Place pins of keystone piston-ring groove
gauge J 29510 opposite each other in
groove to be measured, so they will be held
in position by springs.
Refer to Figure 5-13.
2. Using a four- to five-inch micrometer,
measure distance between outer edges of
two parallel pins. Check each compression
ring groove in two locations: parallel and
perpendicular to wrist pin bore. Record both
measurements.
3. Compare readings with specifications in Fits
and Limits chart in the SPECIFICATIONS
section.
1. Pins 2. Springs
200331
a
1
2
2
1
5-101.bk Page 15 Friday, March 17, 2006 11:05 AM