Detonation on 408 Stroker

If even close to zero deck and flat top piston with 65-63ish cc chamber you are more like 12:1. My x head with IIRC 65 cc chamber with a flat top piston, .010 in the hole is 12.2 to 1 with 5cc valve reliefs. Numbers are just off the top of my head. No pun intended. Not sure what your stock chamber size is.