Valve Lash Adjustment For Cummins Valve lash adjustment is suggested to be done at 150K miles which I think is too far down the road. My valve lash were out of adjustment a bit at 92K miles. So this is how I did my valve lash adjustment on my truck. Valve lash adjustment is fairly simple to do and doesn't require much for tools. Tools Needed: 1. Feeler gauge set (0.010 and 0.020)