I don't think it was the heads but your tune up. oh wait its never the tune up its always the parts fault. the orange crate fed ran 95 percent going over 250mph in a nhra legal vintage dragster. the car set the low et at the march meet one year and runnered up. they ran hot heads for many years before switching to ajs. there are so many cars running hh on nitro I cant count. its not the heads.