I have to check my notes on the venturi sizes on the PF and the Holley I just got and let ya know but I've used em on fairly stout small-blocks and mild big blocks(not my choice)w/good results. The smaller venturi has it's benefits up to a certain point just as the bigger one does but I agree on a Dominator in most applications making 500+ HP big or small-block.............. I don't memorize this stuff cos it hurts my brain..........