340 stroker help?

Is it a solid flat tappet cam?
Sometimes when the lash goes too large it makes the cam act like a smaller cam and bring dynamic compression up. If lash is like .022 or above bring it down to like .016 and see if its better.
Or it just has less than optimum burn in the open chamber from sharp chamber edge or incorrect plug choice.
You certain TDC mark is correct? I have a new balancer that is 4 degress out. Put timing to 38 to get 34 etc but that is alot of cranking compression so maybe the cam is too advanced u could try retard it 4 deg or something