The reason why Hemis dominate the Nitro classes is because they are the only engine with a port design good enough to keep the exhaust valves from melting. During the overlap period enough air goes thru them to cool the exhaust valve for the next stroke.

Take care,
Rick
68 Coronet R/T 440 & 68 Charger 528 Hemi,and 5 Challengers! 6 cyl, 318, 360, 383, 451