I had a guy ask me to help find his engine problem, turned out the Valve seat had fallen out & chewed the head.. So I had them stripped & a reweld around the chewed seat & had a new seat installed. I discussed with a Heat Treatment expert about what I should do with the alloy, he checked them with some fancy hardness tester & told me they were now trash. His verdict was the heads were made of the same junk alloy counterfeit aircraft parts are made from. What ever the alloy is, it goes seriously soft with high heat & does not respond to tempering with heat treatment. That kind defeats the advantage alloy heads have for repair work. Anyway I have a Stealth door stop in my shed these days.