Hummer H2. Manual — part 1828

Move the valve back and forth in the guide. The valve should move freely with no resistance or drag.

Valve and Seat Grinding

Fig. 486: Inspecting Valves For Damage
Courtesy of GENERAL MOTORS CORP.

IMPORTANT:

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Reconditioning the valve seats is very important. The seating of the
valves must be perfect for the engine to deliver optimum power and

2004 Hummer H2

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2

1. Inspect the valve for the following conditions:

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Burnt or eroded areas (1)

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A worn margin (2)

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A bent stem (3)

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A worn or scored stem (4)

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A worn key groove (5)

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A worn stem tip (6)

performance. Several different types of equipment are available for
grinding valve seats.

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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.

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The recommendations of the manufacturer of the equipment should
be followed carefully to obtain the proper results. Regardless of
what type of equipment is used, it is essential that valve guide bores
be free from carbon or dirt to ensure proper centering of the tool
pilot in the guide.

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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.

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Several different types of equipment are available for refacing
valves. The recommendation of the manufacturer of the equipment
should be carefully followed to obtain the proper results.

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DO NOT reface intake valves. Intake valves with excessive wear or
damage MUST be replaced.

2004 Hummer H2

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2

Fig. 487: Inspecting Valve Face
Courtesy of GENERAL MOTORS CORP.

2. Inspect the valve face for the following conditions:

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Worn or no margin (1 or 4)

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Pitted surfaces (2)

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Burnt or eroded areas (3)

2004 Hummer H2

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2

Fig. 488: Inspecting Valve Seating
Courtesy of GENERAL MOTORS CORP.

3. Inspect the valve margin.

The exhaust valve may be refaced if the margin is greater than 1.25 mm (0.05 in) thick before grinding.

2004 Hummer H2

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2