Home » Duramax LLY » Duramax LLY – CYLINDER HEAD OVERHAUL – Disassembly

Duramax LLY – CYLINDER HEAD OVERHAUL – Disassembly

1. Remove glow plugs and injectors if not previously removed.

2. Remove temperature sender from left side head (Figure 2-132).

3. Clean valve faces with wire brush and measure amount valves are recessed in head with dial indicator. Intake valves should be recessed approximately 0.001 in. (0.034 mm) and exhaust valves approximately 0.002 in. (0.048 mm). Recessing means valve faces are positioned below cylinder head combustion chamber surface.
• If valves extend or protrude above chamber surface, engine is equipped with wrong valves, or heads have been mismachined.
• If valves are recessed to at least the stated values, continue with disassembly.

4. Remove valve assembly in sequence as follows:
a. Compress valve spring with compressor tool J–8062 (Figure 2-133).
b. Remove valve locks (Figure 2-134).
c. Release and remove compressor tool.

d. Remove valve retainer, shield and spring.
e. Remove stem seal from valve and slide valve out of guide and head.
f. Remove shim.
g. On exhaust valve, also remove nylon stem and guide seal (Figure 2-134).
h. Remove remaining valve assemblies in same manner.
i. Keep valve parts together on workbench or use yardstick with drilled holes to keep valve assemblies separate.

NOTE: Do not intermix the valve parts as intake and exhaust valve are different. In addition, the exhaust valves have two stem seals and a rotator style spring retainer.

5. Mark position of pre-combustion chambers in each cylinder head (Figure 2-135). Ideally, chambers (if reused), should be installed in same location in head.

6. Remove prechambers from cylinder heads (Figure 2-135). Use a round pry tool to loosen and start each chamber out of seat in cylinder head.

7. Remove cover and gasket from right side head (Figure 2-136).


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