Sunset Racecraft racing engines does not run them and has great luck. Last year at Indy it was said that 75% of the sportsman class had Sunset Racecraft engines. There reasoning is that when you put a stud girdle on it pulls some of the rocker studs to where some are in a bind causing them to fatigue and later brake. Its is true you have a extra lock, but you also have to loosen an extra thing to adjust. But on the contrary, Reher Morrison builds a great engine and uses stud girdles. I believe there reasoning is that it takes the harmonics out of the valve trane that causes fatigue. I have one of each and both are great engines. I've not had to readjust either.