Cummins/Onan QST30 — Valve Adjustment (Overhead Set)
Adjustments · Valve train
For the Cummins/Onan QST30, from the Cummins/Onan owner's manual.
Applies to: Cummins/Onan G-Drive, Cummins/Onan QST30, Cummins/Onan QST30 engine
Before you start
- Use the correct firing order for the engine being serviced or parts will be damaged.
Procedure
- Steam clean engine to prevent dirt entering when covers are removed.
- Remove the rocker lever covers and all related components.
- Rotate engine clockwise until the damper mark aligns with the pointer.
- Identify the cylinder with both valves closed and rocker levers loose.
- Loosen the valve adjusting screw locknut.
- Insert the correct feeler gauge: intake 0.43 mm, exhaust 0.80 mm.
- Tighten locknut to 60 N-m [45 ft-lb] without adapter; recheck clearance.
- Install the rocker lever cover with a new gasket; torque 7 N-m [62 in-lb].
Tools required
- Feeler gauge Amazon
- Torque wrench Amazon
- Inch pound torque wrench 3376592 Amazon
- Torque wrench adapter ST669 Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Intake 0.43 mm [0.017 in]
- Exhaust 0.80 mm [0.032 in]
- Locknut with adapter 45 N-m [35 ft-lb]
- Locknut without adapter 60 N-m [45 ft-lb]
- Rocker lever cover 7 N-m [62 in-lb]
Full service-parts list: Cummins/Onan QST30 →
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.