A lot of heads can flow a lot of air with a small valve. Take for example a small block 1.60 exhaust valve on a TrickFlow head. (240 cfm) Keep in mind a 2.02 Edelbrock intake valve out of the box maxes out at 243cfm on my bench. Way off topic but just using this as an example. Many guys would be happy with a 300cfm big block Edelbrock Head.