I know cfm stands for cubic feet per minute. My question is what does the cfm depend on? Is it the jets or the bores or what? Can you change the cfm of a carb? IF so how do you go about changing it? Im kinda new to carbs so any advice would be appreciated.
Thanks, Danny

 

It refers to the air flow capacity of the carb at wide open throttle. It is tested at a certain pressure drop from inlet to outlet (forget the number off the top of my head).

Most manufacturers rate their carbs with just air. Demon does theirs "wet", meaning they have fuel flowing through the carb as well, but are only measuring the air being pulled through the carb. That method is a little more real-world, but not a big deal, really.

Generally speaking, you don't modify the CFM of a carb, you buy a different one. There are carbs out there that have interchangable venturi so you can modify the flow, but for street cars, that really isn't necessary.

 

4 bbl carbs are rated at 1.5" of vacuum. 2bbl carbs and EFI stuff is rated at 3".

the dry flow vs wet flow thing is really pretty pointless IMO. just means about a 10% difference in the ratings. Demon just does that so that thier carbs test out a litttttttlle bit bettter than Holleys of the same "size". Not because they're actually any better..but because they're really just a little bigger.