How so? From my understanding, my holley 350 2v is bigger than a super six carb (I've heard a BBD flows 280, dunno if that's the slant or 318 one though) but that's all on a different scale than the 4v, (3"hg vs 1.5"hg). Correct me if I'm wrong, but that would make a 350 flow ~240-250, bigger than the BBD but still smaller than the 390 by a bit. I've always heard the 390, 450 and 500 edel were good matches for a mild slant, and that a 600 was for 1hp/CI and more, plus you'd get ~10mpg as well...