Cummins/Onan — Cylinder Head Disassembly
Repair & overhaul · Cylinder head assembly
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Before you start
- Compressed air used for cleaning will not exceed 30 PSI (207 kPa).
Procedure
- Steam clean head and dry with compressed air.
- Secure head to holding fixture.
- Compress valve springs one at a time.
- Remove half collets, spring seats, springs, and valves.
- Remove pipe plugs from fuel passages.
- Hot tank clean heads for four hours.
- Clean internal fuel passages with brush.
- Sand bottom surface with orbital sander to 125 R.M.S.
Tools required
- ST-583 holding fixture Amazon
- ST-448 valve spring compressor Amazon
- ST-876 fuel passage cleaning brush Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
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.