Holley 500 CFM 2 Barrel #0-4412S on a Slant 6
His "calculations" are dead wrong. 500 CFM is 500 CFM. Math does not lie. It's all in how that CFM is delivered that makes the four barrel different.
"500 cfm is 500 cfm" IF measured at the same vacuum.
I seem to remember that Holley uses a different amount of vacuum on their flow bench when they test 2-barrells as opposed to 4-barrel carbs.
I don't have the numbers, offhand, and it seems to be a self-defeating thing for Holley to do, but years ago, I ran across that information. It was valid then; I doubt if Holley has changed their M.O. in the meantime...
I'll try to get some more definitive information, tomorrow, but for now, I don't think that a 500 cfm 2 bbl Holley carb will flow as much air as a 500 cfm Holley 4-Barrel, because of the different vacuum values used by Holley to rate them.
Could be wrong... been wrong before!!!!:pale:
Oh... check this out.
Look at page 77 on
http://tinyurl.com/4n8bfdz
Scroll down using the "ghost" arrow on the left, for an explanation (COMPARING CARBURETOR FLOW CAPACITY) that states, basically, that 1- and 2-bbl Holley carbs are rated at 3 hg. vacuum, while 4bbl carbs are only rated at 1.5 Hg vacuum; apples and oranges. Sounds to me like there's no direct comparison.
There's an example there that shows that a 500 cfm Holley 2bbl equals the flow of a 344 cfm Holley 4 bbl...
What do you think?