i built many engines .some for mud some for hill and hole .and many other forms of racing and stuff you take out on nice days and beat the hell out of it . there is tricks over the years that can help BUT you can not go cheap on valve train parts . and i would never run a HYD cam in a mud runner.good machine work is a good start .some guys say there PROS but still just do not get it... or do not care .i just took down a HI rent race engine and the valve springs were sliding off the spring shims cutting in the heads. the valve seals were holding the springs they shimed them past the spring cups engine was running at 8000 around the track and the valve springs were trying to flip over so the $300 valve springs were junk one had a small amount of bend from this