I don't want to offend anyone either, but I agree, it's pretty unbelievable that carb swap could change the HP output that much. Sounds like the dyno went way out of calibration while the carbs were being swapped. I swapped a 4150 onto my 464 ci while on the dyno and gained about 7 HP over the EPS800, probably would have gained another 7 if I put on a Q-jet.

I have custom made pistons, forged H beam rods, steel crank, ported high flow aluminium heads. ported high rise, matched exhaust, roller cam and rockers, and I make just over what you have with a basic stock engine and a carb swap? I know one dyno differs from the next, could get 500 on dyno 'A' and 535 on dyno 'B', but 100HP change with a box stock holley? I hope when Oldskool wins the lottery and has lots of money, he sends me one of those carbs as well. I'd like an easy way to move up to 635HP.

Sounds like something got bumped or tweeked on the dyno calibration.

No offense intended, just my thoughts on those numbers.