Duramax LLY – CYLINDER HEAD OVERHAUL – Cylinder Head Reassembly

1. Scuff sand all gasket surfaces with 180 grit paper.

2. Clean the valvetrain parts and cylinder head with solvent and dry with compressed air.

3. Install new freeze plugs in heads if necessary. Apply Permatex #2 or high temp adhesive/sealer to edges of plugs before installation. Be sure plugs are properly seated.

4. Install combustion prechambers in cylinder heads (Figure 2-142). Chambers should be flush to no more than 0.002 in. (0.05 mm) above head surface.

5. Install new nylon stem and guide seals on exhaust valve guides.

6. Lubricate valve stems and guides with 30w engine oil, or assembly lube.

7. Install valves as follows (Figure 2-142):
a. Insert valve into guide and through nylon seal on exhaust valves.
b. Install shim.
c. Lubricate and install stem seal on valve.
d. Position valve spring and damper on shim.
e. Install shield followed by retainer on valve spring.
f. Compress spring with spring compressor tool (Figure 2-133).
g. Install valve locks. Be sure locks are fully seated before proceeding. Use petroleum jelly to hold locks in place during installation.
h. Release and remove compressor tool.

8. Check valve spring installed height:
a. Use dividers and micrometer or vernier caliper (Figure 2-143).
b. Measure height from bottom of spring to top of shield as shown.
c. Correct height is 46 mm (1.81 in.). Height can exceed specified figure by 0.127 mm (0.005 in.) but must never be lower than specified.
d. Use thicker shim to decrease height, or thinner shim to increase height Replace any valve spring that can not be set to specified height.

9. Apply Permatex #2, or high temp sealant to threads of coolant temperature sender. Then install the switch in the left head (Figures 2-132 ).

10. Install access cover and gasket, if removed. Use Permatex #2 or high temp sealant on gasket.

11. Cover assembled heads if they will not be installed immediately.


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