GM Service Manual Online
For 1990-2009 cars only

Tools Required

    • J 8089 Carbon Removal Brush
    • J 8001 Dial Indicator Set
    • J 9666 Valve Spring Tester
    • J 28410 Gasket Remover

    Object Number: 797550  Size: SH

    Notice: Carefully clean the aluminum gasket surfaces in order to prevent damage to the sealing surfaces. Use only plastic, wood, or dull gasket scrapers, such as J 28410. Follow the manufacturer's recommendations to dissolve gasket materials with chemical agents.

  1. Remove all gasket material from the sealing surfaces using the J 28410 .

  2. Object Number: 4957  Size: SH
  3. Use the J 8089 to clean the carbon from the combustion chambers.

  4. Object Number: 797551  Size: SH
  5. Using a valve guide bushing brush and solvent, clean all the valve guide bushings.
  6. Using a soft brush and solvent, clean the cylinder head:
  7. • Intake and exhaust parts
    • Intake and exhaust valve seats

    Object Number: 264683  Size: SH
  8. Inspect the cylinder head for flatness. Using a straight edge and a feeler gage, measure the surfaces contacting the cylinder block and manifolds for warpage. Refer to Engine Mechanical Specifications . If the warpage is greater than the maximum, replace the cylinder head.
  9. Inspect for the following in the cylinder head:
  10. • Cracks in the exhaust ports
    • Cracks in the combustion chambers
    • Cracks to the water jackets
    • Cracks in the valve seats
    • Valve seats for looseness

    Object Number: 156174  Size: SH
  11. Use a buffing wheel to clean the valve stems and the valve heads.
  12. Inspect the valves for the following:
  13. • Burnt or damaged areas (1)
    • Undersized valve margin (2)
    • Bent stems (3)
    • Scoring or other damage to the stem (4)
    • Worn key groove (5)
    • Worn stem tip (6)

    Object Number: 156173  Size: SH
  14. Inspect the valve contact surface for the following conditions:
  15. • Undersized margin (1)
    • Pitted surface (2)
    • Burnt or eroded areas (3)
    • Acceptable edge, margin, (4)

    Important: Minor imperfections of the valve may be corrected during reconditioning.

  16. Valves with excessive damage must be replaced.

  17. Object Number: 719136  Size: SH
  18. Perform the following steps to inspect the valve stem, 1 to valve guide, 2 clearance:
  19. • Clamp the J 8001 on the exhaust port side of the cylinder head.
    • Locate the indicator so the movement of the valve stem crosswise to cylinder head will cause a direct movement of the indicator stem.
    • Drop the valve head 10 mm (0.39 in) off the valve seat.
    • Using light pressure to move the stem of the valve side to side to obtain a clearance reading. Refer to Engine Mechanical Specifications .

    Object Number: 797552  Size: SH
  20. Measure the valve stem in 3 locations if the valve clearance is out of specifications.
  21. • Replace the valve if the valve stem is out of specification.
    • Ream the valve guide and use an oversized valve if the valve stem is within specification.

    Object Number: 40075  Size: SH
  22. Inspect the valve springs for broken coils or coil ends.
  23. Perform the following steps to inspect the valve for squareness:
  24. • Place the valve spring on a level surface next to a square.
    • Rotate the valve spring.
    • Replace the valve spring if the valve spring is more than 1.58 mm (0.062 in) out of square.

    Object Number: 4960  Size: SH
  25. Using calipers, measure the free length of the valve spring. Refer to Engine Mechanical Specifications .
  26. Use the J 9666 in order to measure the valve spring force. Refer to Engine Mechanical Specifications .