Quote:

This is the roller motor 5.9L Magnum with a .520/.544 Hughes cam, stock lifters/valvetrain/pushrods, RHS heads, and stock valves.
Not even a .010" feeler gauge fits between the valve stem and rocker arm


For starters with a hydraulic roller lifter motor you should have preload not lash and you should therefore not be able to any feeler gauge between the rocker and valve stem.
Did you use the valve springs that are compatable withthat cam lift and did you check for coil bind. Alos did you check to make sure that you have enough cleanarance between the valve spring retainer and the valve guide and seal so that it does not hit. In boththe above instances you need at least (preferabley more) .060 more travel at full valve lift if you don't you have potential problems and could very well do as you have explained your problem.