Cummins/Onan JWC4-10S-3 — Reassembling Cylinder Head
Repair & overhaul
For the Cummins/Onan JWC4-10S-3, from the Cummins/Onan service manual.
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Before you start
- Tighten cylinder head screws and nuts in the sequence shown in Fig. 22.
Procedure
- Install valve springs with closed coils up against cylinder block.
- Install valves in proper seats and insert valve spring locks.
- Adjust valve tappet to valve stem clearance to .014 in.
- Bring cap screws and nuts down finger tight, then torque in sequence.
- Set spark plug electrode gaps at .030 in and install plugs.
- Install manifold with new gaskets and exhaust pipe with new gasket.
- Install governor, adjust governor belt tension, connect oil supply line.
- Recondition ignition unit, set ignition timing, install upper radiator hose and fill cooling system.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Cylinder head screws 65 to 75 foot pounds (740 to 920 inch pounds)
- Cylinder head nuts 60 to 65 foot pounds (720 to 780 inch pounds)
Source: Cummins/Onan 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.