When I look for aftermarket roller cams, the only ones you can find in jegs, and summit havel ifts of at least .480, why do they do this and not say anything about machining your old head to work with it, on stock heads i am told the max is about .460, or is the max lift on a factory roller motor's head capable of more lift than non roller heads.

When i do this kind of installation, im gonna put the appropriate springs in with the cam, if i use the correct spring with the bigger cams, will it work in the stock head without hitting the top of the valve guides.

 

They prolly assume that you're going to use aftermarket heads that deserve a big cam. I figure that using a cam with that much lift in stock heads would be a waste of time.

Think of it as "valve train Darwinism". If the heads can't handle that much lift then it will destroy everything forcing you to get heads that can handle it

I wouldn't count on stock heads to handle much past .460-.480 lift....from what I've heard and seen.