I've contacted Comp Cams about the lifter noise. Of course their answer to the problem was to replace the lifters. Another sale for them. I was asked if when I put thumb pressure on the rocker arm at the push rod does the tapping increase? Well I had done that and the tapping did increase. They say the lifters are probably defective , be it a mechanical problem or possibly dirt in the lifter. My question is should a hydraulic lifter compress with just thumb pressure ?