I had issues with the valves that came with mine tuliping .
Was supposedly caused by excessive spring psi and egt. 140 seat, 1500-1600* egt.
After a rebuild, it was Ferrea valves, new seats, as the originals were loose.
Guides were gone. A couple were loose. All within <1000 mi on the street.
My machinist guy was aware of "issues" with the head design.
Champion said head stud torque was causing the columns to shift, distorting the chamber.
AIRC, Canfield was making the castings, and reportedly had mold changes that needed to be made to help with the column issues. Not known if that was ever done.
Stage 2 application.