I am looking for some one who has changed the cam in there zz502 crate motor. I am in the process of rebuilding my 502
and am looking for a cam that will work with this motor without
modifing pistons for valve clearance. I am looking at the Crane
hyd. roller with 610 lift and 112 center line but am afraid this may
cause interference with piston to valve.

I've done this three times now. I use the Crane 168741 cams, with the matching crane lifters and push rods. All my pistons are still stock with no clearance problems. I run B&M 250 blowers...

Thanks for the info. what comp. ratio are you running with the blowers, are you overdriving or underdriving your blower at.
and are you using the aluminum heads with this setup.

I'm using the GM square port heads so compression is 8.75 to 1. I upgraded the valves to Inconel. The springs and retainers ae Isky. Boost is 4-5#.