GM Service Manual Online
For 1990-2009 cars only

Tools Required

    • J 8087 Cylinder Bore Gage
    • J 42385-100 Head/Main Bolt Thread Repair Kit
  1. Clean the following areas:
  2.    Notice: Do not use a caustic solution to clean the aluminum engine block.

       Important: When cleaning an engine block in a thermal type oven, do not exceed 232°C (450°F).

    • The engine block in the solvent
    • Remove all sludge, dirt, or debris. Refer to Cleanliness and Care .

    Caution: Wear safety glasses in order to avoid eye damage.

    • Dry the block with compressed air.
    • The gasket surfaces
    • Refer to Replacing Engine Gaskets .
    • The coolant passages
    • The oil galleries
    • The main bearing caps
    • The engine block head bolt holes for threadlocking material
    • Thread repair tool J 42385-107 may be used to clean the threads of old threadlocking material.
  3. Inspect the following areas:
  4. • The cylinder walls for excessive scratches, gouging, or ring ridge
    • The coolant jacket for cracks
    • The valve lifter bores for excessive scoring or wear
    • The crankshaft bearing webs for cracks
    • The gasket sealing surfaces for excessive scratches or gouging
    • Refer to Replacing Engine Gaskets .
    • The oil galleries for restrictions
    • All threaded bolt holes for damage
  5. Measure the cylinder bores for oversize.

Measuring the Cylinder for Oversize


    Object Number: 4974  Size: SH
  1. Adjust the micrometer to 99.0 mm (3.897 in).
  2. Insert the J 8087 into the micrometer and zero the bore gauge dial.

  3. Object Number: 4972  Size: SH
  4. Use a bore gage and measure the cylinder bore for oversize.
  5. Slide the bore gage up and down throughout the length of the cylinder bore. Check the bore both parallel and perpendicular to the centerline of the crankshaft.

    A cylinder that measures 99.0-99.018 mm (3.897-3.898 in) may be honed and serviced with a standard size piston.

    A cylinder bore that exceeds the maximum diameter must be serviced with an oversized piston.