I'm running Hughes rollers on a .509 Purple shaft and at 1/2 turn, lifter compressed, they are as quiet as a mouse. Did you check your sweep pattern of the roller across the valve face through an entire valve closed/open/closed cycle. This needs to be done with a solid lifter or adjustable hydraulic (Hughes sells them) and as long as all the valve stem heights on both heads are the same I'd check both valves on No. 1 and 2 cylinders.