Cummins/Onan — Valves - Adjustment
Adjustments · valve train
From a Cummins/Onan owner's manual covering: 6C8.3, 6CT 8.3, 6CTA8.3. Check it applies to your exact model before use.
Applies to: Cummins/Onan 6CTA8.3, Cummins/Onan C Series, Cummins/Onan 6CT8.3 engine
Before you start
- Be sure to disengage the engine timing pin after locating TDC
Procedure
- Remove air crossover tube, support clamps and crankcase vent tube.
- Remove the valve cover.
- Locate Top Dead Center for cylinder number 1 using barring gear and timing pin.
- Check/set valves with engine cold, below 60C [140F].
- Adjust the valves indicated for STEP A (intake then exhaust).
- Tighten locknut to 24 Nm [18 ft-lb] and re-check valve lash.
- Rotate crankshaft 360 degrees; be sure timing pin is disengaged.
- Set the valves indicated for STEP B; tighten locknuts to 24 Nm [18 ft-lb].
Tools required
- Screwdriver Amazon
- 13, 14, 15 and 18 mm wrenches Amazon
- Feeler gauge Amazon
- Barring gear Part No. 3904682 Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Intake clearance 0.30 mm [0.012 inch]
- Exhaust clearance 0.61 mm [0.024 inch]
- Rocker lever locknut 24 Nm [18 ft-lb]
Full service-parts list: Cummins/Onan C Series →
Source: Cummins/Onan owner's 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.