Engine like that doesn't need more than 600 cfm but a 750 vac secondary won't hurt anything. The 750 will probably never fully open since that engine will only use 500 to 500 cfm of air at WOT.
Really, 500 cfm? Wonder why the six pack worked so well on the 440, 1350 cfm. They also worked on the 340 engine.
Six pack doesn't flow 1350 cfm, that is a 2bbl rating number not a 4bbl rating number. Engine output of 400 hp requires 569 cfm with a BSFC of 0.500. If the engine is more efficient than 0.500 then it requires even less air to make 400 hp.
Okay, let's do the math on a six pack; center carb is a 350 cfm, the two end carbs flow 500 cfm each. I hope I don't need to add this up for you. Go on youtube and go to Nick's Garage and watch a 440 six pack on his Super Flow dyno. He has a camera looking down the carbs, now tell me they aren't completely open at WOT.
