Generac — Cylinder Head Installation
Repair & overhaul
From a Generac service manual covering: IM100G, IM80G, NP100G, NP80G. Check it applies to your exact model before use.
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Before you start
- DO NOT rotate crankshaft and camshaft separately or valves will hit the piston heads.
Procedure
- Set No. 1 cylinder at TDC of its compression stroke by aligning the CAMSHAFT TIMING PULLEY MARK with the mark on the main bearing cap.
- Install camshaft assembly. Note positioning of camshaft front face when No. 1 cylinder is at TDC.
- Measure camshaft end play with thermostat housing and gasket installed.
- Install rocker shaft with rocker arms.
- Install bolt stoppers. Always use NEW bolt stoppers.
- Install cylinder head with a new gasket. Always use a new cylinder head gasket; use washers between bolts and head.
- Tighten cylinder head bolts in sequence: first to 22 ft-lbs (29 N-m), then 47 ft-lbs (64 N-m), loosen completely, tighten to 22 ft-lbs (29 N-m), then to 47-51 ft-lbs (64-69 N-m).
- Install timing belt and oil pump idler and oil pump regulator spring. Install upper dust cover.
- Tighten upper dust cover bolts to 2.9-3.6 ft-lbs (4-5 N-m).
- Install spark plugs and tighten to 14-22 ft-lbs (20-29 N-m).
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
Source: Generac service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.