GM Service Manual Online
For 1990-2009 cars only

Tools Required

J 8087 Cylinder Bore Checking Gauge

  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 cylinder head bolt holes for threadlocking material
    • Thread repair driver 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 following areas:
  6. • The cylinder bores for taper
    • The cylinder bores for excessive ring ridge at the top of the cylinder

Measuring the Cylinder for Taper, Out-of-Round, and Oversize


    Object Number: 4974  Size: SH
  1. Adjust the micrometer to 99.0 mm (3.897 in).

  2. Object Number: 4972  Size: SH
  3. Insert the bore gauge into the micrometer and zero the bore gauge dial.
  4. Use a bore gauge and measure the cylinder bore for taper, out-of-round, and oversize.
  5. Slide the bore gauge 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 bore 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.