Chevrolet Silverado / GMC Sierra. Manual — part 165
3. Use the J 5830-3 in order to ream the exhaust valve guide in order to achieve the correct
valve stem-to-guide clearance.
4. Always recondition the exhaust valve seat after reaming the exhaust valve guide bores and
installing new exhaust valves.
measure the valve stem-to-guide clearance, the valve stem-
to-guide clearance is not within specifications.
2008 Chevrolet Silverado 1500
2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado
Fig. 551: Identifying Inspection Points For Valves Damage
Courtesy of GENERAL MOTORS CORP.
5. Inspect the valves for the following:
Burnt or damaged areas (1)
Undersized margin (2)
Bent stem (3)
Scoring or other damage to the stem (4)
Worn key groove (5)
Worn stem tip (6)
2008 Chevrolet Silverado 1500
2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado
Fig. 552: Inspecting Valve Face For Burning, Pitting & Cracking
Courtesy of GENERAL MOTORS CORP.
6. Inspect the valve contact surface for the following:
Undersized margin (1)
Pitted surface (2)
Burnt or eroded areas (3)
2008 Chevrolet Silverado 1500
2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado
Acceptable edge margin (4)
Valves with excessive damage must be replaced.
Minor imperfections of the valve or valve seat may be repaired.
7. Reconditioning of the valves and valve seats:
The valves must seat perfectly for the engine to deliver optimum power and
performance.
Cooling the valve heads is another important factor. Good contact between each valve
and valve seat in the cylinder head is necessary to insure that the heat in the valve head
is properly carried away.
Regardless of what type of equipment is used, it is essential that the valve guide bores
are free from carbon or dirt in order to ensure the proper centering of the pilot in the
valve guide.
The valve seats should be concentric to within 0.05 mm (0.002 in) total indicator
reading.
Reface pitted valves on a valve refacing machine in order to ensure the correct
relationship between the valve head and the valve stem.
Replace the valve if the valve stem is excessively worn or warped.
Replace the valve if the edge margin (4) of the valve head is less than 0.79 mm (0.031
in) thick after grinding.
Several different types of equipment are available for reconditioning valves and valve
seats. Follow the equipment manufacturer's recommendations for equipment use to
attain the proper results.
CYLINDER HEAD ASSEMBLE
Tools Required
J 8062 Valve Spring Compressor. See Special Tools.
J 42073 Valve Stem Seal Installer. See Special Tools.
Assemble
2008 Chevrolet Silverado 1500
2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado
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