Valve Guide Reaming

Fig 1: Measuring Valve Stem-To-Guide Clearance

Courtesy of GENERAL MOTORS CORP.

CAUTION: 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.

CAUTION: 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.

Using the J 8001: 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 gauge to measure the guide bore.

Fig 2: Valve Stem & Valve Guide

Courtesy of GENERAL MOTORS CORP.

If the clearance measurement between the valve stem (1) and guide (2) is not within specification, the valve and/or the cylinder head must be replaced. Refer to Engine Mechanical Specifications (6.2L LS3) or Engine Mechanical Specifications (6.2L LS9) .

Fig 3: Inspecting Valves For 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.
- If a valve guide is worn or has excessive stem-to-guide clearance, the cylinder head should be replaced.
Measure the valve stem diameter. If the valve stem diameter is not within specification, the valve must be replaced. Refer to Engine Mechanical Specifications (6.2L LS3) or Engine Mechanical Specifications (6.2L LS9) .
If the valve stem diameter is within specifications, and the stem-to-guide clearance is excessive, the cylinder head must be replaced.