Cummins/Onan — Adjust Valve Lash Clearance
Adjustments · Valve train
From a Cummins/Onan owner's manual covering: 6CTA8.3, CFP83-F10, CFP83-F20, CFP83-F30, CFP83-F40. Check it applies to your exact model before use.
Applies to: Cummins/Onan 6CTA8.3, Cummins/Onan CFP83-F10, Cummins/Onan CFP83-F20, Cummins/Onan CFP83-F30, Cummins/Onan CFP83-F40, Cummins/Onan 6CTA8.3G2 engine, Cummins/Onan 6CTAA8.3G3 engine
Before you start
- Be sure to disengage the engine timing pin after locating top dead center to prevent damage to the engine timing pin.
Procedure
- Remove the air crossover tube, support clamps, hose clamp, and wastegate sensing line.
- Remove the crankcase vent tube and remove the valve cover.
- Locate top dead center for cylinder No. 1 by rotating the crankshaft while pressing on the engine timing pin.
- Check/adjust the valves indicated for STEP A (I = intake; E = exhaust).
- Tighten the rocker lever locknut and recheck valve clearance. Torque: 24 N•m [212 in-lb].
- Disengage the timing pin; mark the vibration damper and rotate the crankshaft 360 degrees.
- Set the valves indicated for STEP B; tighten the locknut and recheck the clearance.
- Install a new rubber seal in the valve cover and new sealing o-rings on the capscrews.
- Install the valve cover, wastegate sensing tube, and crankcase vent tube.
Tools required
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 in]
- Exhaust clearance 0.61 mm [0.024 in]
- Check/set valves with engine cold below 60°C [140°F]
- Rocker lever locknut torque 24 N•m [212 in-lb]
Full service-parts list: Cummins/Onan CFP83-F10 →, Cummins/Onan CFP83-F20 →, Cummins/Onan CFP83-F30 →, Cummins/Onan CFP83-F40 →
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.