29. Piston Measurement

1. Clean the piston skirts and the pins with a cleaning solvent. Do not wire brush any part of the piston.
2. Clean the piston ring grooves with a ring groove cleaner. Make sure the oil ring holes and slots are clean.





3. Inspect the pistons for the following conditions:
^ Cracked ring lands, skirts, or pin bosses
^ Ring grooves for nicks and burrs that may cause binding
^ Warped or worn ring lands
^ Eroded areas at the top of the piston (1)
^ Scuffed or damaged skirts (2)
^ Worn or scuffed piston pin bores (3)
4. Replace pistons and piston pins that show any signs of damage or excessive wear.





5. Measure the piston-ring end gap. Place the piston ring in the area of the bore where the piston ring will travel (approximately 120 mm or 4.72 inches down from the deck surface).
6. Square the ring in the cylinder bore by positioning the ring with an inverted piston head.





7. Measure the piston ring end gap with feeler gauges. If the end gap is greater than specifications replace the piston ring.
Top Compression Ring End Gap: 0.20-0.35 mm (0.0079-0.0137 inch)
Maximum Top Compression Ring End Gap: 0.70 mm (0.0276 inch)
Second Compression Ring End Gap: 0.35-0.50 mm (0.0138-0.0196 inch)
Maximum Second Compression Ring End Gap: 0.70 mm (0.0276 inch)
Oil Ring End Gap: 0.20-0.70 mm (0.0079-0.0275 inch)
Maximum Oil Ring End Gap: 1.8 mm (0.0709 inch)





8. Measure the piston ring side clearance. Roll the top two piston-rings entirely around the piston ring groove. If any binding is caused by the ring groove, dress the groove with a fine file. If any binding is caused by a distorted piston ring, replace the ring.
9. With the piston ring on the piston, use feeler gauges to check clearance at multiple locations.
10. If the clearance is greater than specifications, replace the piston ring.
11. If the new ring does not produce the correct side clearance, replace the piston.
Top Compression Ring Side Clearance: 0.030-0.070 mm (0.0012-0.0027 inch)
Second Compression Ring Side Clearance: 0.020-0.060 mm (0.0008-0.0023 inch)





12. Measure piston-to-cylinder bore clearance. Using an outside micrometer, measure the width of the piston 26.5 mm (1.04 inch) below the top of the piston at the thrust surface perpendicular to the centerline of the piston pin.
13. Subtract the measured piston diameter from its original cylinder bore diameter.
Piston-to-Cylinder Bore Clearance: 0.02-0.04 mm (0.0008-0.0015 inch)
14. If the clearance obtained through measurement is greater than specifications and the cylinder bores are within specification, replace the piston. If the cylinder bores are not within specification, rebore all 4 cylinders and fit with oversize pistons. Select the smallest available oversize pistons.
Standard Size Pistons: 83.970-83.990 mm (3.3059-3.3066 inch)
0.25 mm (0.0098 inch) Oversize Pistons: 84.220-84.240 mm (3.3157-3.3165 inch)
0.50 mm (0.0196 inch) Oversize Pistons: 84.470-84.490 mm (3.3256-3.3263 inch)