Chevrolet Silverado / GMC Sierra. Service manual — part 343

Clean the following components:

Remove all sludge, dirt, or debris using a cleaning solvent or thermal type oven. Refer to
Cleanliness and Care.

Gasket surfaces

Refer to Replacing Engine Gaskets.

Coolant passages

Oil galleries

Main bearing caps

Cylinder head bolt holes to remove threadlocking material

Thread repair tool J 42385-107 may be used to clean the threads of any residual
threadlocking material.

Inspection Procedure

1. Inspect the following components:

Cylinder walls for excessive scratches, gouging, or ring ridge

Cylinder bores for excessive ring ridge at the top of the cylinder

Coolant jacket for cracks

Valve lifter bores for excessive scoring or wear

Crankshaft bearing webs for cracks

Gasket sealing surfaces for excessive scratches or gouging

Refer to Replacing Engine Gaskets.

Oil galleries for restrictions

Threaded bolt holes for damaged threads

Cylinder bores for excessive ring ridge at the top of the cylinder

2. Measure the cylinder bores for an oversize condition:

Measuring the Cylinder for Oversize

IMPORTANT: When cleaning the engine block in a thermal type oven, do not

exceed 232°C (450°F).

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2

Fig. 391: Measuring Bore Gauge With Micrometer
Courtesy of GENERAL MOTORS CORP.

1. Adjust the micrometer to a dimension slightly smaller than the bore size. Refer to Engine

Mechanical Specifications.

2. Insert the J 8087 into the micrometer and zero the bore gage dial. See Special Tools.

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2

Fig. 392: Measuring Cylinder Bore
Courtesy of GENERAL MOTORS CORP.

3. Use the J 8087 and measure the cylinder bore for oversize. See Special Tools.

Slide the bore gage up and down throughout the length of the cylinder bore. Measure the
bore, both parallel and perpendicular to the centerline of the crankshaft, at the top, center,

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2

and bottom of the bore. A cylinder bore that exceeds the maximum diameter must be
serviced with an oversized piston. Refer to Engine Mechanical Specifications.

CYLINDER BORING AND HONING

Boring Procedure

1. Measure all pistons with a micrometer to determine the cylinder bore diameter.

2. Before you use any type of boring bar, use a fine file and clean the top of the cylinder block,

removing any dirt or burrs. If you do not check the cylinder block, the boring bar may be
improperly positioned or tilted and the cylinder bore could be bored at an incorrect angle.

3. Carefully follow the instructions furnished by the manufacturer regarding use of the

equipment.

4. When you bore the cylinders, ensure all the crankshaft bearing caps are in place. Tighten the

crankshaft bearing caps to the proper torque in order to avoid distortion of the cylinder
bores during final assembly.

5. When you take the final cut with a boring bar, leave 0.03 mm (0.001 in) on the cylinder

bore diameter for the finish honing and fit of the piston.

Honing Procedure

IMPORTANT: A 0.5 mm (0.02 in) oversize service piston and a piston ring

set are available.

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2