valve to piston clearance
I would suggest that you take a little time and do a valve to piston clearance check. If you have two touching, you have more very close or touching. It doesn't matter what cam, lifters or pistons you are running. You don't have enough clearance. A little time spent now is a lot less than the time and money you will spend fixing a valve head that went through a piston.
speaking from experience,
gyrogearloose