Valve Guide Reaming

WARNING: This page is about a different car, the 2007 Hummer H2. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Measuring Valve Stem-To-Guide Clearance

Courtesy of GENERAL MOTORS CORP.

IMPORTANT:

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.
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.

Measure the valve stem-to-guide clearance using a dial indicator. 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.

Fig 2: Inspecting For Excessive Valve Stem To Guide Clearance

Courtesy of GENERAL MOTORS CORP.

A valve stem (1) and guide (2) with excessive clearance must be replaced or the components replaced. Refer to Engine Mechanical Specifications .

Fig 3: Identifying Inspection Points For Valves Damage

Courtesy of GENERAL MOTORS CORP.

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.
Measure the valve stem diameter. A valve stem with a diameter less than 7.95 mm (0.313 in) 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.