What it boils down to is shrouding of both valves, intake and exhaust. Both valves in the wedge combustion chamber have shrouding, restricting flow. They are shrouded by the chamber along with the cylinder itself when the valve's open. The Hemi chamber doesn't have this problem, they are getting the full use of their valves and ports with no shrouding. This is the reason they came out with the canted valve heads, to alleviate some of the shrouding of the wedge head design.