GM Service Manual Online
For 1990-2009 cars only

Important: Measurements of all components should be taken with the components at normal room temperature.

For proper piston fit, the engine block cylinder bores must not have excessive wear or taper.

A used piston and pin set may be reinstalled if, after cleaning and inspection, they are within specifications.


    Object Number: 895472  Size: SH
  1. Inspect the engine block cylinder bore. Refer to Engine Block Disassemble in this section.
  2. Inspect the piston and the piston pin. Refer to Piston, Connecting Rod, and Bearing Cleaning and Inspection in this section.

  3. Object Number: 895494  Size: SH
  4. Use a bore gage and measure the cylinder bore diameter. Measure at a point 64 mm (2.5 in) from the top of the cylinder bore.
  5. Measure the bore gage with a micrometer and record the reading.

  6. Object Number: 895114  Size: SH
  7. With a micrometer or caliper at a right angle to the piston, measure the piston 14 mm (0.57 in) from the bottom of the skirt.
  8. Subtract the piston diameter from the cylinder bore diameter in order to determine the piston-to-bore clearance.
  9. Proper piston-to-bore clearance is 0.01-0.041 mm (0.0006-0.0016 in).
  10. • If proper clearance cannot be obtained, select another piston and measure the clearances.
    • If proper fit cannot be obtained, hone the cylinder bore or replace the cylinder block.
  11. When the piston-to-cylinder bore clearance is within specifications, mark the top of the piston using a permanent marker for installation to the proper cylinder.