Chevrolet Silverado / GMC Sierra. Manual — part 164

Fig. 548: Measuring Valve Stem-To-Guide Clearance Using J 8001
Courtesy of GENERAL MOTORS CORP.

10. Measure the valve stem-to-guide clearance.

Excessive valve stem-to-guide clearance may cause an excessive oil consumption and may
also cause a valve to break. Insufficient clearance will result in noisy and sticky functioning
of the valve and will disturb the engine assembly smoothness.

1. Clamp the J 8001 on the exhaust port side of the cylinder head.

2. Position the dial indicator so that the movement of the valve stem from side to side,

crosswise to the cylinder head, will cause a direct movement of the dial indicator stem.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado

The dial indicator stem must contract the side of the valve stem just above the valve
guide.

3. Drop the valve head about 1.6 mm (0.063 in) off the valve seat.

4. Use light pressure and move the valve stem from side to side in order to obtain a valve

stem-to-guide clearance reading. Refer to Engine Mechanical Specifications .

VALVE GUIDE REAMING, AND VALVE AND SEAT GRINDING

Tools Required

J 5830-02 Valve Guide Reamer Set. See Special Tools.

Servicing

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado

Fig. 549: Inspecting For Excessive Valve Stem To Guide Clearance
Courtesy of GENERAL MOTORS CORP.

1. Measure the valve stem-to-guide clearance. Refer to Cylinder Head Cleaning and

Inspection.

2. Improper valve stem (1) to valve guide (2) clearance may cause excessive oil consumption.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado

Fig. 550: Reaming Exhaust Valve Guide Using J 5830-3
Courtesy of GENERAL MOTORS CORP.

CAUTION: Refer to SAFETY GLASSES CAUTION .

IMPORTANT: Exhaust valves with excessive valve stem-to-guide clearance

must be replaced with the available service valve that has an
0.774 mm (0.0305 in) oversize valve stem. The intake valves
are NOT available with oversize valve stems. Replace the
cylinder head if after using a NEW intake valve in order to

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado