Cummins/Onan — Remove and Install Cylinder Head (C and J Series)
Repair & overhaul
From a Cummins/Onan service manual covering: V12 Series, V6-140, V6-200, V6-VAL, V6-VIM, V8-185, V8-265, V8-350, V8-VALE, V8-VINE, VT12, VT8-430. Check it applies to your exact model before use.
Applies to: Cummins/Onan V12 Series
Before you start
- Three different sets of cylinder head capscrews may be used on J Series engines; they are not interchangeable.
- Do not let machined surfaces become scratched or marred.
Procedure
- Remove rocker lever cover, manifolds, generator, thermostat housing, fuel manifolds, injectors.
- Loosen all cylinder head capscrews; remove center capscrews and insert short capscrews as guides.
- Remove rocker lever assembly; remove push tubes.
- Attach lifting fixtures; remove head from block.
- Remove and discard cylinder head gasket, grommets and retainers.
- Installation: place gasket on block with 'Top' stamp up.
- Install grommets and grommet retainers.
- Lower head slowly so both ends touch gasket at the same time.
- Install push tubes; largest is center injector push tube.
- Install rocker lever assembly using short capscrews as guides.
- Install long capscrews through rocker lever bearings.
- Lubricate capscrews with Shell Rust Preventive-ENSIS-105 or equivalent.
- Tighten cylinder head capscrews in sequence to values in Table IX.
- Install injectors; adjust injector plungers then valves.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Tighten to Table IX values in sequence
Full service-parts list: Cummins/Onan V12 Series →
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.