Chevrolet Silverado / GMC Sierra. Manual - part 369
1. Using a dial indicator, measure the valve stem-to-guide clearance. Position the tip of the dial
indicator at the top of the valve guide.
Valve stem-to-guide clearance may also be obtained by using a micrometer to measure the
valve stem diameter and a ball type measuring gage to measure the guide bore.
NOTE:
Excessive valve stem-to-guide clearance may cause a noisy
valve train, premature valve stem oil seal wear, component
damage, and/or excessive engine oil consumption.
NOTE:
Insufficient valve stem-to-guide clearance will result in noisy
or sticking valves. Valves that are too tight may disturb engine
smoothness or lead to component damage.
2008 Hummer H2
2008 ENGINE Engine Mechanical - 6.2L - H2
Fig. 479: Inspecting For Excessive Valve Stem To Guide Clearance
Courtesy of GENERAL MOTORS CORP.
2. A valve stem (1) and guide (2), with excessive clearance, must be replaced or the cylinder
head replaced. Refer to Engine Mechanical Specifications.
2008 Hummer H2
2008 ENGINE Engine Mechanical - 6.2L - H2
Fig. 480: Identifying Inspection Points For Valves Damage
Courtesy of GENERAL MOTORS CORP.
3. Inspect the valve stems for excessive scoring, wear, or warpage.
A valve stem that has excessive scoring (3 or 4) or wear (4 or 6) must be replaced.
If a valve guide is worn or has excessive stem-to-guide clearance, the cylinder head
should be replaced.
4. Measure the valve stem diameter. A valve stem with a diameter less than 7.95 mm (0.313 in)
2008 Hummer H2
2008 ENGINE Engine Mechanical - 6.2L - H2
must be replaced.
If the valve stem diameter is within specifications, and the stem-to-guide clearance is
excessive, the cylinder head must be replaced.
Valve and Seat Grinding
Fig. 481: Identifying Inspection Points For Valves Damage
Courtesy of GENERAL MOTORS CORP.
2008 Hummer H2
2008 ENGINE Engine Mechanical - 6.2L - H2