Valve to piston clearance ?

how much stretch is there in the valve train when it heats up?

When Jim/IQ52 competed in the engine masters Mopar muscle challenge, this other guy with a 361 had his valve hit his 361 piston and blow up the motor. I assume that he did a valve to piston check...? is this limit pushed with these kind of builds?

If I recall it didn't hit the piston it was clipping the cylinder wall ,the 361 has a small bore at 4.12" compared to a 400 at 4.34