Hummer H1 (1992-1998). Manual - part 19

2-21. CYLINDER HEAD AND VALVE REPAIR (Cont’d)

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2-21. CYLINDER HEAD AND VALVE REPAIR (Cont’d)

9. Install valve (2) in valve guide (4) from which it was removed.

CAUTION

Clearance must be 0.001-0.003 in. (0.026-0.076 mm). Excessive

valve stem clearance will cause excessive oil consumption and may

cause valve breakage.

NOTE

● 

Intake and exhaust valves are available with 0.0035 in.

(0.089 mm) and 0.0137 in. (0.349 mm) oversize stems.

● 

If valve stem clearance is more than 0.0027 in. (0.068 mm), valve

guide must be reamed to next size and oversized valve installed.
If unable to produce clearance with oversize valve, replace
cylinder head.

10. Using dial indicator, measure valve stem clearance. Dial indicator must contact valve stem (1) just

above valve guide (4) and at a right angle to the valve stem (1). Drop valve (2) approximately

1/16 in. (1.6 mm) off valve seat (3) and move side-to-side when taking measurement.

11. Repeat steps 9 and 10 for remaining valves (2) and valve guides (4).
12. Inspect cold start advance switch (6) and engine temperature sending unit (5) for damage. Replace

if damaged. 

d. Refacing Valves

1. Using valve face grinding machine, grind valve face (7) on all valves (2) to 45”.

2. Maintain a minimum of 1/32 in. (0.80 mm) margin (8) on all valves (2). If margin falls below

specifications, replace valve.

e. Grinding Valve Seats

1. Using valve seat grinding kit, grind all valve seats (3) to 46°.

NOTE

If valve seat width exceeds specifications, valve seat width must

be narrowed.

2. Measure width of intake valve seats (3). Valve seats (3) must not be wider than 1/16 in. (1.53 mm).
3. Measure width of exhaust valve seats (3). Valve seats (3) must not be wider than 3/32 in. (2.36 mm).

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2-21. CYLINDER HEAD AND VALVE REPAIR (Cont’d)

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2-21. CYLINDER HEAD AND VALVE REPAIR (Cont’d)

f. Assembly

1.

2.

3.

4.

5.

6.
7.

8.

9.

10.

NOTE

For general assembly instructions, refer to para. 2-12.

Apply OE/HDO to exhaust valve (18) and install valve (18) in valve guide (15) from which it was

removed.

NOTE

● 

Valve caps on exhaust valves are rotaters.

● 

Perform step 2 for 6.5L engines and 1990 and above

6.2L engines. Perform step 3 for previous model 6.2L
engines.

Install seal (21), valve spring shim (14), valve spring (13), valve stem seal (12), shield (11), and valve
cap (9) on exhaust valve (18).

Install valve spring shim (14), valve spring (13), shield (11), and valve cap (9) on exhaust valve (12).

Using spring compressor, compress valve spring (13) and install valve seal (10) in groove (17)
in exhaust valve (18) and install valve keys (8). Slowly release spring compressor.
Apply OE/HDO to intake valve (19) and install valve (19) in valve guide (16) from which
it was removed.
Install valve spring shim (2), valve spring (3), shield (4), and valve cap (6) to intake valve (19).
Using valve spring compressor, compress valve spring (3) and install valve seal (5) in groove (20)
in intake valve (19) and install valve keys (7). Slowly release spring compressor.
Check installed height of valve springs (3) measuring from top of valve spring shim (2) to top
of shield (4).

Spring height must be 1-13/16 in. (46 mm). If spring height is greater, remove valve spring (3)
and add spring shim(s) (2) to bring spring height within specifications.
Repeat steps 1 through 9 for remaining valves and opposite cylinder head.

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