Chevrolet Silverado / GMC Sierra. Service manual — part 368

1. Clean the following components:

Use the J 8089 in order to remove the carbon from the combustion chambers. See
Special Tools.

Gasket surfaces

Refer to Replacing Engine Gaskets .

Valve stems and heads on a buffing wheel

Bolt hole threads

Remove all dirt, debris, or threadlocking material from the bolt holes.

2. Inspect the cylinder head for the following conditions:

1. Cracks in the exhaust ports and combustion chambers

2. External cracks in the water chambers

3. Gasket surfaces for excessive scratches or gouging

Refer to Replacing Engine Gaskets .

4. Bolt hole threads for debris or damaged threads

Refer to Thread Repair or Thread Repair Specifications .

IMPORTANT:

When cleaning a cylinder head in a thermal type oven,
do not exceed 204°C (400°F).

Be careful not to scuff the chamber.

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2

Fig. 476: Inspecting Cylinder Head For Warpage
Courtesy of GENERAL MOTORS CORP.

3. Inspect the cylinder head for warpage. Refer to Engine Mechanical Specifications.

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2

Fig. 477: Measuring Valve Spring Tension
Courtesy of GENERAL MOTORS CORP.

4. Use the J 9666 in order to measure the valve spring tension. See Special Tools. Refer to

Engine Mechanical Specifications.

VALVE GUIDE REAMING, AND VALVE AND SEAT GRINDING

Tools Required

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2

J 37378-1 Valve Guide Reamer. See Special Tools.

Valve Guide Reaming

Fig. 478: Measuring Valve Stem-To-Guide Clearance
Courtesy of GENERAL MOTORS CORP.

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2