AJ, I could very well be wrong about the Fox .60 running hot because of what I did to the head. I've had no issues with your heads and none with any other Davis equipped engine. I now have another Fox .60 and another Davis head I got from a friend, I also have head shims to use if needed, Fox makes them. As my learning curve increases I've learned that the Diesels run much smoother and cooler if I back the compression down about 100 rpm from absolute peak rpm and run the idle needle slightly rich from the best idle.