500 CFM

[Andy302]

Question.

Is a 500cfm carb big enough for a Ford 302 with full Edelbrock performer kit? Used Motor math and the formula under tricks & tips etc to work it out at 5,500 rpm.

Anyone running a 500 or 600 on thie engine with stories to tell?

Cheers guys

Andy R
Proper Planning Prevents Piss Poor Performance! :7

[craigh]

I think the carbs are matched to the engine by a specific formula which calculates the cfm,im sure some of the guys here will know this.
I have a 500cfm carb fitted to my 302 mated to an eidlebrock torker 2 inlet recommended to me by brian at roadcraft uk who said this was the baby for me

[Bowtie]

Carb theory is quite straight forward. The engine need air for combustion. The higher volume and rev. the higher the need for air. There are other aspect that will make a difference like volumetric efficency (VE) and manifold caracteristics.

The most important thing is to realise the difference between a steet engine and a race engine. What works on the track might not be so practical in a general traffic situation. Street engines must performe over a much wider spectrum and the easiest fault you might do if you try to mimic the race engine is to go for a too large carb, because it will make your car bog! You can compensate with either a longer accellerator pump shot and/or more fuel shot if you are slightly over-carbed. If you are grossly over-carbed you will NEVER get the needed vacuum signal to the boosters!

That's why you should calculate the maximum need for your engine, multiply with VE, and pick a carb based on that CFM need (no more and no less). Spread bore and vacum secondarys will help drivability and fuel consumtion...

[STEVE G]

Edelbrock recomend the 500 for upto 305cui and with the tuning kit I'm sure it will be more than man for the job,unless you're building a full race engine.
Steve G {-}
GE427-Rover 281ci.(300+BHP)

[Bowtie]

>I think the carbs are matched to the engine by a specific
>formula which calculates the cfm,im sure some of the guys here
>will know this.

Taken from the Holley web site:

Engine Size (CID) x Maximum RPM / 3456 = CFM @100% Volumetric Efficiency

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

Approximately 608 CFM would be required for this engine. However, most street engines are capable of achieving only about 80% VE; a modified street engine with ported heads, headers, good intake and carburetor can achieve about 85% VE; a fully modified race engine can achieve 95% or greater VE. The CFM number arrived at with this formula must be factored by this percentage.

[Andy302]

Thanks to all.

I didnt want to over fuel the thing!

Andy R
Proper Planning Prevents Piss Poor Performance!