They are good heads and I used both versions. They flow 410-430 intake side with B1 originals and make around 1000-1040 HP on 540 and up CI engines. The B1/MC's flow 440-455 intake side, and should make around 1040-1100 with the right combo and 572 or more CI. Compression should be 14.5-1 or more for the higher HP. If you want the mack daddy power, go Predator and don't fool around. They are capable of over 1200HP with flow #'s over 500 CFM.
Those numbers are a little conservative, if the engine is built right. But yes, 1000+ hp is pretty common for B1 heads, either version.
