What does adjusting the valves do? How can you tell if you need it? How is it done? I am totally clueless on this, I thought only motorcycles needed valve adjustments.

 

The Cummins does not have hydraulic tappets, so the valve clearance must be set by hand. There has to be some clearance in the valvetrain or you will burn a valve, but too much clearance will cause parts to get pounded to death. The usual clue to needing a valve adjustment is that you can hear the valvetrain clattering as you roll down a hill. Cummins says to do it every 25k.

You can increase top end performance by setting them a little tighter than spec, this increases the effective duration of the cam.

There's info in the sticky about how to do it, so I won't get into that here.

 

Thanks. Sounds like I need to give it a look.