I have mainly tried them in pump gas engines around 500 cu in, and in those cases they haven't worked very well. They have huge ports compared to teh flow, which means low velocity. The ones I built did not make enormous power and were a bit shy on tq too. Even if they flow better than some others, I propably wouldn't use them except in all out engines. Different story with more cubes, I guess. And will find out, there is a set that made 780 hp on a 500 going on a 604 short block. We'll see....