I thought the x heads were the better/flowing performing head, not the j heads? so it is cfm of the heads that determines how much lift you can run in the cam?
Well no, you need them to flow at least to .050 less than max lift of cam.jmo
As in, if the heads don't flow past .450 lift, then a .550 lift cam is a wash no matter how much opening/under curve flow there is[to a certain point] the valve is held open during the reversion stage too long and will hurt performance.
