Fitting Pistons & Rings
NOTE:
Pistons and rings are available in .01 mm and .02 mm oversize.
- Inspect cylinder block for cracks or flaws. Using bore gauge, measure for out-of-round or excessive taper. If measurements exceed .0008" (.020 mm), refinish bore. When one cylinder is bored, all must be bored. Check head gasket surface for warpage. Maximum limit is .002" (.05 mm).
- Determine piston oversize according to cylinder wear. Standard bore diameter is 3.1890-3.1902" (81.000-81.030 mm). Bore wear limit is .008" (.20 mm). Measure piston diameter at right angle to pin and .20" (5 mm) below oil ring groove. Add piston-to-cylinder clearance. Determine finish hone of cylinder.PISTON DIAMETER SPECIFICATIONS
Application In. (mm) Standard 3.1846-3.1850 (81.890-81.900) 0.01 mm Oversize 3.1850-3.1554 (80.900-80.910) 0.02 mm Oversize 3.1854-3.1858 (80.910-80.920) - After honing cylinder to final fit, measure piston-to-cylinder clearance with parts at 70°F (20°C). Ensure difference of bore limit between cylinders is .002" (.05 mm) or less. If beyond limit, cylinders must be bored.
- If reusing pistons, de-carbon ring grooves with scraper and curved steel wire or piece of broken ring. Clean oil slots in bottom land of oil ring groove. Check for scratches, wear or damage.
- Measure side clearance of rings in grooves as each is installed. Check ring end gap. Install ring squarely in cylinder, using piston. If beyond limits, replace piston and/or rings. When installing rings, ensure code mark faces up. See Fig 1.