Not much use to you now, but in future with a flat tappet, don't use high Zinc oil AND a Zinc additive. You probably ended up with at least 4 times the minimum needed PPM of ZDDP, if not more, and excess ZDDP has been reported to cause other issues like spalling. Those issues started showing up with a bit over 2x the old levels of ZDDP.
With the stud problems, I am curious as to how much spring pressure you are using and your max RPM's?
