Chapters

Handbook / Maintenance / Valve lash

Chapter 3 Maintenance

Valve lash (overhead adjustment)

Valve lash is the small clearance in the valve train. On adjustable Cummins engines it is checked and set at intervals; Cummins calls it the overhead adjustment.

5.9L Cummins in a Dodge Ram with the valve cover off, showing the rocker arms
A 5.9 Cummins with the valve cover off. The rocker arms are where lash is set on adjustable engines. Photo: Dana60Cummins, CC BY-SA 3.0 (resized), via Wikimedia Commons.

What it is

Valve clearance changes as parts wear. Too tight or too loose and the engine can run poorly or get noisy. On adjustable engines a technician checks and sets it with feeler gauges, using the engine maker's procedure and clearances.

Which engines

  • Older B-series engines (12-valve, 24-valve, 5.9 common rail and earlier 6.7) have adjustable valve trains.
  • Cummins says the 2019 and later chassis-cab 6.7 uses hydraulic lash adjusters that eliminate the overhead adjustment, and its motorhome guide shows no adjustment for those newer engines.

Where this comes from

Last reviewed 2026-10-19. General information only: your owner's manual and service information come first.