Hummer H1 (1992-1998). Manual - part 18

2-20. TIMING GEAR COVER REPAIR (Cont’d)

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2-21. CYLINDER HEAD AND VALVE REPAIR

This task covers:

a. Disassembly

d. Refacing Valves

b. Cleaning

e. Grinding Valve Seats

c. Inspection

f. Assembly

INITIAL SETUP

Tools

General mechanic’s tool kit:

automotive (Appendix E, Item 1)

Valve spring compressor

(Appendix E, Item 22)

Bench grinder (Appendix E, Item 23)
Rotary wheel wire brush

(Appendix E, Item 24)

Electric drill (Appendix E, Item 25)
Rotary end wire brush (Appendix E, Item 26)

Valve spring tester (Appendix E, Item 27)
Straightedge (Appendix E, Item 15)
Feeler gauge (Appendix E, Item 13)
Dial indicator (Appendix E, Item 10)

Valve face grinding machine

(Appendix E, Item 28)

Valve seat grinding kit (Appendix E, Item 29)

Materials/Parts

Sixteen valve seals (Appendix D, Item 47)
Water jacket cover gasket (Appendix D, Item 20)
Lubricating oil OE/HDO (Appendix B, Item 13)
Pipe sealing compound (Appendix B, Item 17)

Manual References

Equipment Condition

Engine disassembled into subassemblies
(para. 2-15).

NOTE

The cylinder head and valve repair procedures for 6.5L engines, 1990 and
above 6.2L engines and previous model engines are basically the same.

Any differences in procedures are noted. Refer to engine decal model

number on left rocker arm cover before ordering replacement parts.

a. Disassembly

1.

2.

3.
4,
5.

6.

7.

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Using valve spring compressor, compress intake valve spring (3) and remove valve keys (7).
Release valve spring compressor slowly.
Remove valve cap (6), shield (4), valve spring (3), valve spring shim (2), and valve seal (5) from
intake valve (16). Discard valve seal (5).

NOTE

Valves must be installed in the same location they were removed from.
As each valve is removed, place on numbered board or stand.

Remove intake valve (16) from cylinder head (1).
Repeat steps 1 through 3 for remaining intake valves.
Using valve spring compressor, compress exhaust valve spring (13) and remove valve keys (8).
Release valve spring compressor slowly.

NOTE

● 

Valve caps on exhaust valves are rotaters.

● 

Perform step 6 for 6.5L and 1990 and above 6.2L engines only. 6.5L

engine has another seal as indicated in step 6.

Remove valve cap (9), shield (11), valve stem seal (12), valve spring (13), valve spring shim (14),
seal (17), and valve seal (10) from exhaust valve (15). Discard valve seal (10).
Remove valve cap (9), shield (11), valve spring (13), valve spring shim (14), and valve seal (10) from
exhaust valve (15). Discard valve seal (10).

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

NOTE

Valves must be installed in the same location they were removed

from. As each valve is removed, place on numbered board or stand.

8. Remove exhaust valve (15) from cylinder head (1).
9. Repeat steps 5 through 8 for remaining exhaust valves.

NOTE

Precombustion chambers must be installed in the same location they
were removed from. Mark precombustion chambers for assembly.

10. Remove four precombustion chambers (18) from cylinder head (1).
11. Repeat steps 1 through 10 for opposite cylinder head.
12. Remove engine temperature sending unit (19) from left cylinder head (1)
13. Remove cold start advance switch (20) from right cylinder head (1).

14. Remove two capscrews (21), water jacket cover (22), and water jacket cover gasket (23) from right

cylinder head (1). Discard gasket (23).

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2-21. CYLINDER HEAD AND VALVE REPAIR 

(Cont’d)

 b. Cleaning 

1. Using bench grinder and rotary wheel wire brush, clean all valve stems (2) and valve heads (3).

2. Using drill motor and rotary end wire brush, clean all combustion chambers ( 12) and intake and

exhaust ports (13).

3. Refer to para. 2-9 for additional cleaning information.
4. Repeat steps 1 through 3 for opposite cylinder head.

 c. Inspection 

1.

2.

3.

4.

5.

6.
7.

8.

NOTE

For general inspection instructions, refer to para. 2-10.

Inspect valves (1) for cracks, scoring, galling, and burned heads (3). Replace valves (1) if cracked,
scored, galled, or if heads (3) are burned.
Inspect valve springs (8) and dampers (7) for damage. Replace valve spring (8) if either are
damaged.
Inspect valve caps (5), shields (6), valve spring shims (9), and valve keys (4) for damage. Replace
if damaged.
Remove dampers (7) from valve springs (8). Using valve spring tester, compress valve spring (8)

to 1-13/16 in. (46 mm). If pressure is less than 70 lb (311 N), replace valve spring (8). Compress
valve spring (8) to 1-25/64 in. (35 mm). If pressure is less than 220 lb (978 N), replace valve
spring (8). Test remaining springs in same manner. Install dampers (7) into springs (8).
Inspect cylinder head (11) for cracks in valve ports (13) or combustion chambers (12) and external
cracks to the coolant chamber (14). Replace cylinder head (11) if cracked.

NOTE

Precombustion chamber is available in standard and oversize.
If replacing a precombustion chamber, check for marking "OS”
on precombustion chamber. If marking is present, oversize pre-
combustion chamber must be used.

Inspect precombustion chambers (10) for cracks or damage. Replace if cracked or damaged.
Inspect cylinder head (11) mating surfaces for scratches or dents. Replace cylinder head (11) if
scratched or dented deeper than 0.003 in. (0.076 mm).
Using a straight edge and feeler gauge, check flatness of cylinder head to block mating surface.
Flatness of cylinder head (11) must not vary more than 0.002-in. (0.051 mm) in distance of 6 in.
(15.2 cm), or more than 0.006 in. (0.152 mm) overall. Replace cylinder head (11) if flatness does not
meet specifications.

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