The better question is why did they not put the 440 CID short block under the hemi heads??? There wouldn't be any of this stupid debate about 426 hemi vs 440 6bbl, the hemi would have had the TQ like a 440 6 pack PLUS the top end of the hemi.
NASCAR had a 427 cubic inch rule. 7.0 liters. That’s why there are so many mid 60’s engines that size.
A 440 couldn’t run in NASCAR
406 ford
410 mercury
413 mopar
421 pontiac
425 Buick
426 mopar
427 ford chev
The reason for the 440+6 VS the hemi debate is the huge valves and ports on the hemi give away bottom end. So the Sox pack is out front early. The hemi was designed for nascar racing, it’s is a racing engine on the steeet.
