Does anybody know how much valve lift can be run before you start to run into piston to valve clearances on a stock Mark VI 454? This is the 330hp flat top piston, oval port head, low compression motor. I know I can pull a head and check it with modeling clay, i'm just hoping someone has already done their homework so I don't have to.!? Thanks.!

Alright guys, how bout me putting it this way. What cam have you guys been running on these motors with the stock short block and haven't run into any problems....?? Anybody with some lifts in the .540 range????

Would be alot easier to just remove a valve spring and install a real light checking spring and roll it over starting around 15* BTDC and checking until around 15* ATDC.

Besure to have the piston at TDC when removing the spring thou.

I ran an Erson 228/236 degree cam at .050" and it had .542" lift and I had .080" on the intake and way over .100" on the exhaust. The heads were "049" oval port castings with 118 cc combustion chambers with 2.19" intake valves and 1.88" exhaust valves. Hope this helps, but you should check it anyway.

224,232,.527,.553 with 114 deg sep. Advanced 4 degrees. 781 large oval port heads with large valves, flat top pistons. Also had .080 on the intake, exhaust was large.

oopss forgot to mention, that was with an .018 thick head gasket and angle cut heads. stock would have been much more clearance.