5-101.bk Page 15 Friday, March 17, 2006 11:05 AM Inspection Keystone Ring Groove Check 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. 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). Do not stamp or engrave on TOP of piston. Doing so will reduce piston life. 1 2 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. 2 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. 1 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. 200331a Figure 5-12 — Ring Groove Gauge 1. Pins 2. Springs 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.
Do not file or grind chrome-plated piston rings. This may cause chrome to flake, resulting in ring failure. 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. Page 5-15 200 BENCH PROCEDURES