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Home›Repair guides›Cummins/Onan›Intake & Exhaust Valve Procedure

Cummins/Onan — Intake & Exhaust Valve Procedure

Adjustments · Cylinder head / valves

From a Cummins/Onan owner's manual covering: GTA8.3, GTA8.3 CD1, GTAR 3. Check it applies to your exact model before use.

Applies to: Cummins/Onan GTA8.3 engine

Before you start

  • Make sure that the timing pin is disengaged. If the engine is started with the pin engaged, the pin will break and can result in engine damage.

Procedure

  1. Remove the air crossover tube (water-to-air system only).
  2. Disconnect the support clamps, hose clamps, and remove the vent tube.
  3. Remove the valve cover.
  4. Locate top dead center (TDC) for cylinder No. 1 by observing the marks on the vibration damper.
  5. Use a feeler gauge to check or set clearance: intake 0.30 mm [0.012 inch], exhaust 0.61 mm [0.024 inch].
  6. Check or set valves with the engine cold (below 60 C [140 F]).
  7. After finding TDC for cylinder No. 1, use a flathead screwdriver and set the listed intake and exhaust valves.
  8. Tighten the locknut using a torque value of 24 N.m [18 ft-lb]; check the valve lash again.
  9. Mark the vibration damper and rotate the engine 360 degrees.
  10. Set the remaining listed valves with a flathead screwdriver.
  11. Tighten the locknut using a torque value of 24 N.m [18 ft-lb]; check the valve lash again.
  12. Install the rubber seal into the groove in the valve cover; start at the overlap area and do not stretch the seal.
  13. Install the valve cover using a torque value of 24 N.m [18 ft-lb].
  14. Install the crankcase vent tube and secure with support clamps and hose clamp.
  15. Install the air crossover tube (water-to-air only).

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 inch]
  • Exhaust clearance 0.61 mm [0.024 inch]
  • Locknut torque 24 N.m [18 ft-lb]
  • Valve cover torque 24 N.m [18 ft-lb]

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.

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