Cummins/Onan — Cylinder Head Reassembly and Torque Sequence
Repair & overhaul
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan HGJAA, Cummins/Onan HGJAB, Cummins/Onan HGJAC, Cummins/Onan HGJAD, Cummins/Onan HGJAE, Cummins/Onan HGJAF
Procedure
- Lap each valve until uniform ring shows on valve face.
- Apply oil to valve stems and install new valve stem seals.
- Check head dowel pins and install new head gaskets.
- Torque head bolts to 7.2 lb-ft (9.8 Nm) first step.
- Torque to 14.5 lb-ft (19.6 Nm) second step.
- Torque to 24.6-30.4 lb-ft (33.3-41.2 Nm) third step.
- Assemble push rods and rocker arms.
- Adjust valve lash.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Head bolts 7.2, 14.5, then 24.6-30.4 lb-ft in three steps
Full service-parts list: Cummins/Onan HGJAA →, Cummins/Onan HGJAB →, Cummins/Onan HGJAC →, Cummins/Onan HGJAD →
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.