tappin noise after predator 212 engine gets to operating temp.

Hey guys I have a modded predator 212 hemi head that after I installed a dyno 310 cam (I’ve been running the motor with a cm265 cam with everything else’s the same, the only thing I changed was the cam and deepened the valve reliefs in the piston) has started making a tapping noise and will start running rough and shut off. Everything is clearanced, nothing is hitting anywhere, ive taken it apart several times and checked for abnormal where and if something may be hitting on all parts everything from the crank to cam to lifters to push rods to valves, rockers, piston, cylinder bore etc, everything and it all looks good. I can start it back up after a min or so and it’ll run fine for a min or so but start tapping again and will shut off if I can’t pull the plug wire in time. I’m running stock size stainless valves with 36 pounds springs with automotive style keepers and cm push rods, 1.2 nr rockers. I can start it and run it up to 9k on the stand and it’s fine until it gets to operating temp, what’s going on? I’ve been building engines of all types and sizes for years but this has me stumped.
It sounds like you need just a little more valve clearance, .001" to .002" might be enough. The tapping is caused by the valve smacking against the seat when the plug fires and cylinder pressure hits the valve.