The OS LA series
I didn't ry and get 640 out of the OS 40LA, i don;t know what it makes but my guess is it probably makes around 2-2.5 hp at 21k rpm. The big block is for a full size car, i spoke with my buddy and he said that unless you were running a top fueler drag car you'd never see 6000 hp in a 500ci with just NO2. By the way, what the heck is a concrete engine?? Top fuelers are limited to 500ci, and run on straight nitromethane making in the range of 7500hp for about 6 secs until kaboom, something blows.