sure that equation is a ballpark guess.....if your thinking inside the box....step outside...

yes that equation is the general.....for people who just want to bolt on and go....

vacuum secondaries are all varaible....the air being drawn in pulls the door open..only as much as it needs......

now.....lets jump outside the box.....lets say on a normal 350 the engine is only going to move a certain amount of air thru the cylinder according to bore and stroke.... as you know as the piston moves from TDC to BDC and the volume of air it draws in isn't goin to change.....now that same amount of air flows thru the carb...same amount regardless of cfm.....If you get diiferent size carbs to flow the correct air/fuel ratio for that amount of air...any carb will work....."If you only listen to what your taught you'll never be smarter than your teacher" me 89'

I do not mean to bust anyones chops.... you will how ever notice that a 795cfm Q-jet will not flow any more air or fuel than a 600cfm Holley or Edelbrock because all 3 have vacuum secondaries and the Q-jet having the smallest primaries will give him the best results all across the board....

What makes the later 2 a better option is when more idle fuel is needed...as the Q-jet has smaller idle passages and needs modifacation to work with larger cams (230+ dur@.050)....

what I am not saying is you will have the same throttle responce from a 850cfm Holley double pumper as you would from a 500cfm vac sec carb.....out of the box......

To the newbies....Carb tunning/modding is and art....better left to the pro's....

By all means do not go buy a 850 Holley to put on a motor where a 2 barrel once was or even a stock 4 barrel.....these larger carbs or more race oriented than stock calibrated.....

basic rule of thumb.....

small blocks big blocks

4500rpm 500cfm 600cfm
5500rpm 650cfm 750cfm
6500rpm 750cfm 850cfm
7500rpm 750-850cfm 850-950cfm
8500rpm 850-950cfm 950-1050cfm

This is just the basic......