Carb Size Help

[basementdweller]

I\'ve seen a few posts for guys askin what size carb they should use, here\'s a pretty accurate formula that can help you decide what size to go with.



Engine Size(Cubes) X Maximum RPM / 3456 = CFM @ 100% volumetric efficiency



EXAMPLE: 350 CID X 6000RPM = 2,100,000 / 3456 = 608CFM rounded to 600CFM

[Brett]

um...what he said

[Brett]

wait,how comes nobody ever told me that before,that would have taken alot of guess work out of it,thanks onesicks10!!!I cant believe as long as ive been a mechanic that I never knew that.

[basementdweller]

[360hp350]

That formula says the new 572 if it can pull 6500 RPMs needs a 1075 CFM!

[basementdweller]

On 2003-02-02 18:03, 360hp350 wrote:

That formula says the new 572 if it can pull 6500 RPMs needs a 1075 CFM!





it seems accurate.. says my motor would require about 850cfm ... my buddies 434 that spins to 8000 requires 1000cfm.. hes running an 1150 .. it may not be EXACT but itll get ya DAMN close.. you can factor in other things like.. nitrous...



Millenium Yellow Mike

406sb

9:1, mild cam

11.40@116MPH

<img src=http://www.OneSickS10.com/calvin3.gif width=100>

With great power, comes great responsibility.

[rudedogg]

one sick is so on the money with that one,many people use too big of a carb or misunderstand what the use of a specific engine needs,to top it off his s10 runs hard,i have spent the last 13years with efi but i started with the carbs and been through many in my day http://www.s10v8.com/images/smilies/icon_biggrin.gif

[Zack]

The thing is that the formula is for motors that run at 100% volumetric efficiency. If they don\'t (and almost none do - so says the edelbrock catalog) they don\'t need all that cfm. I have no idea where my 2002 edelbrock catalog is at, but in there I think it explains at what volumetric efficiency a 350 runs at with different setups. A 100% volumetric efficient 350 may require 608 cfm to run at 6000 rpm\'s, but a stock or mild 350 is nowhere near 100% volumetrically efficient, so it wouldn\'t require 600 cfm at 6000.

[rudedogg]

lets see nascar runs 600cfm carbs restricter plates,500++++++hp,9000rpm hmmmm,sounds easy to me to decide what to use on a street car