GM Service Manual Online
For 1990-2009 cars only

Special Tools

EN-8087 Cylinder Bore Gauge

For equivalent regional tools, refer to Special Tools.


    Object Number: 2026761  Size: SH
  1. Clean the sealing material from the gasket mating surfaces (2).
  2. Clean the engine block (1) and lower crankcase in a cleaning tank with solvent appropriate for aluminum.
  3. Flush the engine block with clean water or steam.
  4. Clean the oil passages.
  5. Clean the blind holes.
  6. Spray the cylinder bores and the machined surfaces with engine oil.
  7. Inspect the threaded holes. Clean the threaded holes with a rifle brush. If necessary, drill out the holes and install thread inserts.

  8. Object Number: 2026762  Size: SH

    Note:  DO NOT attempt to machine the lower crankcase to engine block surfaces.

  9. Use a straight edge and a feeler gauge to check the deck surface (1) for flatness. Refer to Engine Mechanical Specifications.
  10. If the deck surface is out of specification, replace the block. DO NOT machine the block.

  11. Inspect the oil pan rail for nicks. Inspect the front cover attaching area for nicks. Use a flat mill file to remove any nicks.

  12. Object Number: 2026763  Size: SH
  13. Clean the sealing material from the gasket mating surfaces on the lower crankcase engine block side (1).

  14. Object Number: 2026764  Size: SH
  15. Clean the sealing material from the gasket mating surfaces on the lower crankcase oil pan side (1).

  16. Object Number: 2026766  Size: SH
  17. Inspect the crankshaft main bearing bores. Use the EN-8087 gauge  (1) to measure the bearing bore concentricity and alignment.
  18. Replace the engine block and bed plate if the crankshaft bearing bores are out of specification.

  19. Object Number: 2026767  Size: SH
  20. Inspect the cylinder bores using the EN-8087 gauge  (1). Inspect for the following items:
  21. • Wear
    • Taper
    • Runout
    • Ridging
  22. Refer to Engine Mechanical Specifications for specifications.
  23. If the cylinder bores are out of specification, replace the block.