1. Inspect the valve for the following conditions:
Burnt or eroded areas (1)
A worn margin (2)
A bent stem (3)
A worn or scored stem (4)
A worn key groove (5)
IMPORTANT:
Reconditioning the valve seats is very important. The
seating of the valves must be perfect for the engine to
deliver optimum power and performance. Several
different types of equipment are available for grinding
valve seats.
Another important factor is the cooling of the valve head.
Good contact between the valve and the seat will ensure
that heat will be properly dissipated.
The recommendations of the equipment manufacturer
should be followed carefully to obtain the proper results.
Regardless of the type of equipment used, it is essential
that valve guide bores be free of carbon or dirt to ensure
proper centering of the tool pilot in the guide.
Valves that are pitted must be refaced to the proper
angle. Valve stems that show excessive wear, or valves
that are warped excessively must be replaced. When a
valve head that is warped excessively is refaced, a knife
edge may be ground on part or all of the valve head due
to the amount of metal that must be removed. Knife
edges lead to breakage, burning or pre-ignition due to
heat localizing on this knife edge. If the edge of the valve
head is less than 1.25 mm (0.05 in) after grinding,
replace the valve.
Several different types of equipment are available for
refacing valves. The recommendation of the equipment
manufacturer should be carefully followed to obtain the
proper results.
DO NOT reface intake valves. Intake valves with
excessive wear or damage MUST be replaced.
2008 Hummer H2
2008 ENGINE Engine Mechanical - 6.2L - H2