I've been learning new things constantly on here, but I still have some things to sort out. The one that is nagging on me right now is the cylinder heads. What is the difference between a 58cc and like 63cc or something. I read that 58 cc gives you a higher compression ratio, making power and mileage better, but how exactly does that work? what is the 58cc part that is measured, the cylinders themselves? And which heads can actually be placed on a stock block without having header and piston clearance problems? And finally, what is the difference between a valve angle job and what does it do?