Auto Racing: Valve Clearance, valve clearance, sarasota fl

Question
why is that the exhaust valve/ intake valve are not of the same size; one is bigger than the other. Why don't they have the same valve clearance?please explain.

Answer
Well- -  for one thing , your engine takes IN a mixture of gas and air, then burns the gas, so there's actually less volume left.  That sounds silly and probably is, but all engines are that way and the difference is usually about 20%.   Of course, the intake mixture is drawn in by vacuum, and the exhaust is forced out by the rising piston .  It sounds like I really can't answer that question accurately. It's something I've been curious about but never thought to ask .   Good one !!! you've stumped me !  But I WILL find out ! Look for a follow up answer.

Dan Liddy
Sarasota, Fl.