Max Lift Stck Heads

[X302LX90X]

What is the largest lift that will clear a stock bottom end? My friend has stock heads with a F cam. I wanted to know if we can put 1.7 cobra roller rocker to give it a little more. I know once you got an aftermarket head this won't work. I thought maybe with the small valves in the stock head it may work.

 

[86bluecobra]

I think you maybe pushing the limit of the heads. The x 303 is a .542 lift cam and according to ford racing web site you may have to notch the pistons to run that cam. If you install 1.7 ratio rockers the F-303 cam lift would be .544 lift. Not piston to valve clearence has a lot to do with duration and the F cam has more duration then the X cam. Only way to know for sure is to isnstall and measure clearence.