Were the "swirl port" differences in the chamber or in the bowl. I can clearly see the chamber difference but not any big difference in the bowls or ports. And, intake only or both?
See I'm not sure....the one person above says that they are not even swirl ports at all....but I do not know for sure.
But those who've got 20-25 horse power gain from older heads....makes you wonder what about the head did that?