The modified retainers. do they do just machine the face of the retainer to shorter the over all length? How much is taken off from the stockers. My retainers thickness or height is .311 thick? The fellow that installed my cam is no longer available to talk to so I'm just trying to figure out a few things that he did with the cam install. Now I have another shop redoing my heads because valve seals keep popping off. also I find out that all my valve guides are shot with only 67k on the orginal motor. I only have aprox 5k on this motor after the cam install and it never has been up to speed as far as performance goes with this xpz package. So it is definitely looking like the heads seem to be my major problem.