GM Service Manual Online
For 1990-2009 cars only

Tools Required

    • J 8037 Ring Compressor
    • J 8087 Cylinder Bore Gage
    • J 41556 Connecting Rod Guide
    • J 45059 Angle Meter

Piston Selection


    Object Number: 1950769  Size: SH

    Important: Measurements of all components should be taken with the components at normal room temperature. For correct piston fit, the engine block cylinder bores must not have above acceptable wear or taper. A used piston, pin, and connecting rod assembly may be installed if, after inspection is within specifications.

  1. With a micrometer at a right angle, measure the piston outside diameter (OD). Measure the diameter 43 mm (1.69 in) from the top of the piston. Refer to Engine Mechanical Specifications.
  2. Record the piston OD.

  3. Object Number: 1954213  Size: SH
  4. Adjust the micrometer to the recorded piston OD.
  5. Insert the J 8087  (1) into the micrometer and zero the gage dial.

  6. Object Number: 1950967  Size: SH
  7. Using the J 8087  (1), measure the cylinder bore inside diameter (ID). Measure at a point 64 mm (2.5 in) from the top of the cylinder.
  8. Record the cylinder bore ID.
  9. Subtract the piston OD from the cylinder bore ID to determine the piston-to-bore clearance. Refer to Engine Mechanical Specifications.
  10. If the correct clearance cannot be obtained, select another piston, pin, and connecting rod assembly and again measure the clearances. If the correct fit cannot be obtained, the cylinder bore may require honing for an oversize piston.

Piston, Pin, and Connecting Rod Installation


    Object Number: 1954117  Size: SH
  1. Liberally lubricate the cylinder walls, piston rings and piston skirts with engine oil.
  2. Important: The piston is directional and must be installed in the cylinder block in the correct direction.

  3. Select the correctly numbered piston/connecting rod assembly for the cylinder. A dot (1) showing proper piston orientation is located on the top of the piston.

  4. Object Number: 1961651  Size: SH
  5. Install the J 41556 to the connecting rod.

  6. Object Number: 1950771  Size: SH
  7. Install the J 8037 onto the piston and compress the piston rings.
  8. Install the piston, pin, and connecting rod assembly into the cylinder bore. Hold the piston ring compressor firmly against the engine block. Using a soft hammer handle, lightly tap the top of the piston until all the piston rings have entered the cylinder bore.

  9. Object Number: 1950772  Size: SH
  10. Use the J 41556  (1) to guide the connecting rod onto the crankshaft journal.
  11. Remove the J 41556  (1) from the connecting rod.
  12. Notice: Refer to Fastener Notice in the Preface section.


    Object Number: 1950773  Size: SH

    Important: The connecting rod and cap must be assembled with the mating surfaces correctly aligned.

  13. Install the bearing cap (3), bearing half (2), and connecting rod bolts (1) to the connecting rod (4).
  14. Tighten

    1. Tighten the bolts a first pass to 20 N·m (15 lb ft).
    2. Tighten the bolts a final pass to 85 degrees using the J 45059 .

    Object Number: 1950775  Size: SH
  15. Measure the connecting rods for the correct side clearance. Refer to Engine Mechanical Specifications.