GM Service Manual Online
For 1990-2009 cars only

Special Tools

EN-8087 Cylinder Bore Gage

Cleaning Procedure

  1. Remove any old thread sealant, gasket material or sealant.
  2. Clean all the following areas with solvent:
  3. • Sealing surfaces
    • Cooling passages
    • Oil passages
    • Bearing journals
  4. Clean all threaded and through holes with solvent.
  5. Warning: Refer to Safety Glasses and Compressed Air Warning in the Preface section.

  6. Dry the engine block with compressed air.

Visual Inspection


    Object Number: 2028132  Size: SH
  1. Inspect the crankshaft bearings journals for damage or spun bearings. The crankshaft bearing journals are not repairable, if the crankshaft bearing journals are damaged the engine block assembly must be replaced.
  2. Inspect all sealing and mating surfaces for damage, repair or replace the engine block assembly if necessary.
  3. Inspect all threaded and through holes for damage or excessive debris.
  4. Inspect all bolts for damage, if damaged replace with NEW bolts only.
  5. Inspect the cylinder walls for cracks or damage. The cylinder sleeves are not serviced separately, if the cylinders are damaged the cylinder block assembly must be replaced.
  6. Inspect the engine block for cracks. Do not repair any cracks. If cracks are found, the cylinder block assembly must be replaced.

Measuring Cylinder Bore Diameter


    Object Number: 2028133  Size: SH
  1. Measure the cylinder bore diameter 37.00 mm (1.457 in) from the deck face using the EN-8087 gage  (1).
  2. Compare your results with Engine Mechanical Specifications.
  3. If the cylinder diameter exceeds the specifications, replace the engine block.

Measuring Cylinder Bore Taper

  1. Measure the cylinder bore along the thrust surfaces, perpendicular to the crankshaft centerline, at 10 mm (0.394 in) below the deck surface using the EN-8087 gage and record your measurement.
  2. Measure the cylinder bore along the thrust surfaces, perpendicular to the crankshaft centerline, at 100 mm (3.936 in) below the deck surface and record your measurement.
  3. Calculate the difference between the 2 measurements. The result will be the cylinder taper.
  4. Compare your results with Engine Mechanical Specifications. If the cylinders exceed the specifications, replace the engine block.

Measuring Cylinder Bore out of Round

  1. Measure both the thrust and non-thrust cylinder diameter at 10 mm (0.394 in) below the deck surface using the EN-8087 gage and record your measurements.
  2. Calculate the difference between the 2 measurements. The result will indicate out-of-round at the upper end of the cylinder.
  3. Measure both the thrust and non-thrust cylinder diameter at 100 mm (3.936 in) below the deck surface. Record your measurements.
  4. Calculate the difference between the 2 measurements. The result will indicate out-of-round at the lower end of the cylinder.
  5. Compare your results with Engine Mechanical Specifications. If the cylinders exceed these specifications, replace the engine block.

Engine Block Flatness Inspection


    Object Number: 2028139  Size: SH
  1. Ensure the engine block decks are clean and free of gasket material.
  2. Inspect the surface for any imperfections or scratches that could inhibit proper cylinder head gasket sealing.
  3. Place a straight-edge (1) diagonally across the cylinder block (2) deck face surface.
  4. Measure at 4 points the clearance between the straight-edge (1) and the cylinder block (2) deck face using a feeler gage.
  5. Compare your results with Engine Mechanical Specifications.
  6. If the warpage is less than 0.06 mm (0.003 in), are none work necessarily.
  7. If the deformation is larger than 0.06 mm (0.00236 in), replace the engine block.