His approach to picking a cam for a max effort race engine is very different than what most engine builders do. I have a couple of high effort engines in the shop at the moment so I'll try some of his tricks. Billy starts with the physical constraints and works backwards. Typically people buy and cam and then see if it fits, or else they buy a cam and kit and bolt it in. Billy says he likes to design a cam around a known, proven valve spring. He also designs around minimum valve to piston clearance on the intake side since the piston will pull the intake charge into the combustion chamber when the piston is very close to the intake valve. And he sorts valve springs by coil bind height and works off of bind height. Most engine builders double check for bind but they don't sort springs by bind height and then set up the valvetrain off the bind height. Of course, what Billy is talking about really only applies to max effort engines. He is working on NHRA class winner type of engine or NASCAR and F1 stuff. Still interesting to see how those guys do stuff even if it isn't needed on the average street rod engine.