GM Service Manual Online
For 1990-2009 cars only

    Object Number: 2017277  Size: SH
  1. Inspect the piston.
  2. Using a gasket scraper, remove the carbon from the top of the piston.

  3. Object Number: 2017278  Size: SH
  4. Using a groove cleaning tool or broken ring, clean the piston ring grooves.

  5. Object Number: 2017279  Size: SH

    Note: Do not use a wire brush.

  6. Using a brush and solvent, thoroughly clean the piston.
  7. Using a micrometer, measure the piston diameter at right angles to the piston pin hole, and at a point 12.6 mm (0.4961 in) from the piston head.
  8. Specification
    Standard piston diameter: 80.461-80.471 mm (3.1677-3.1681 in)

  9. If the diameter is not as specified, replace the piston.
  10. Inspect piston oil clearance.
  11. Subtract the piston diameter measurement from the cylinder bore diameter measurement.
  12. Specification

        • Standard oil clearance: 0.029-0.052 mm (0.0011-0.0020 in)
        • Maximum oil clearance: 0.09 mm (0.0035 in)
  13. If the oil clearance is greater than the maximum, replace all the pistons. If necessary, replace the cylinder block.

  14. Object Number: 2017283  Size: SH
  15. Using a feeler gauge, measure the clearance between a new piston ring and the wall of the ring groove.
  16. If the groove clearance is not as specified, replace the piston.

  17. Object Number: 2017284  Size: SH
  18. Using a piston, push the piston ring a little beyond the bottom of the ring travel, 50 mm (1.97 in) from the top of the cylinder block.

  19. Object Number: 2017285  Size: SH
  20. Using a feeler gauge, measure the end gap.
  21. If the end gap is greater than the maximum, replace the piston ring. If the end gap is greater than the maximum, even with a new piston ring, replace the cylinder block.

  22. Object Number: 2017288  Size: SH
  23. Using a caliper gauge, measure the piston pin bore diameter.
  24. Specification
    Standard piston pin bore diameter: 20.006-20.015 mm (0.7876-0.7880 in)

  25. If the diameter is not as specified, replace the piston.

  26. Object Number: 2017290  Size: SH
  27. Using a micrometer, measure the piston pin diameter in three places (a,b,c).
  28. Specification
    Standard piston pin diameter: 20.004-20.013 mm (0.7876-0.7879 in)

  29. If the diameter is not as specified, replace the piston pin.

  30. Object Number: 2017291  Size: SH
  31. Using a caliper gauge, measure the connecting rod small end bore diameter.
  32. Specification
    Standard connecting rod small end bore diameter: 20.012-20.021 mm (0.7879-0.7882 in)

  33. If the diameter is not as specified, replace the connecting rod.
  34. Subtract the piston pin diameter measurement from the piston pin bore diameter measurement.
  35. Specification

        • Standard oil clearance: -0.001 to +0.005 mm (-0.00004 to +0.0002 in)
        •  Maximum oil clearance: 0.010 mm (0.0004 in)
  36. If the oil clearance is greater than the maximum, replace the connecting rod. If necessary, replace the piston and piston pin as a set.
  37. Subtract the piston pin diameter measurement from the connecting rod small end bore diameter measurement.
  38. Specification

        • Standard oil clearance: 0.00-0.011 mm (0.0002-0.0004 in)
        • Maximum oil clearance: 0.014 mm (0.0006 in)
  39. If the oil clearance is greater than the maximum, replace the connecting rod. If necessary, replace the connecting rod and piston pin as a set.

  40. Object Number: 2017296  Size: SH
  41. Using a connecting rod aligner and feeler gauge, check the connecting rod alignment.
  42. Check for misalignment.
  43. Specification
    Maximum misalignment: 0.05 mm (0.0020 in) per 100 mm (3.94 in)

  44. If the misalignment is greater than the maximum, replace the connecting rod.

  45. Object Number: 2017297  Size: SH
  46. Check for twist.
  47. Specification
    Maximum twist: 0.15 mm (0.0059 in) per 100 mm (3.94 in)

  48. If the twist is greater than the maximum, replace the connecting rod.