Carb CFM on a 304ci

Have you all researched something to the point that nothing makes sense anymore? I have a '73 w/304, Eddy performer intake & Eddy 600cfm carb. Based on the threads I've read, and using the formulas, I've determined that for my engine (304ci, 5000 rpm's, & 75% VE) I need ~453cfm. Does this mean I may be over carbed? And could this be a source of low vacuum (not low-low, just not as high as I think it should be. ~18 and holds fairly steady.) I'm thinking the 470 Truck Avenger (yes, I've read the threads. ) may be a suitable size, based on calculations.
I'm not trying to resurrect a "Which carb is best?" thread, that's been hashed out numerous times. I'm just wondering, are my calculations sound?
Happy Monday all... mad: Mondays, blech!)

 

I went from a 600cfm 4bbl to a 1.08 motorcraft 2100 and would say the only better way to go would be fuel injenction. Of course I got all the info I needed from this site!

Kent

 

I get 329 cfm.

304 / 2 * 5000 / 1728 * 0.75 = 329

 

I didn't do any math, but also have a Eddy performer manifold and got the 500 cfm thinking at slow speeds it wouldn't starve for air. The edelbrock tech recommended 500 cfm for my application, which gave me an independently obtained warm and fuzzy.

 

Now you folks have got me thinking....If the 500 cfm is right (is it?) for the 304 then would a 600 cfm be right for a 360? I've got a Holley 600 cfm laying around I thought I'd use on my 360 (mid-range cam, edelbrock performer intake, headers, HEI distributor, stock heads & pistons) but was thinking about getting a new carb.

 

See... Told you my brain was going to mush.R)
Thanks, Tim... I trust your numbers much better than my own. And if anyone is wondering why I used 5000rpm, it was based on my driving, I cruise the freeway at 3200 tops. I figure if this motor hits 7000, I done broke something!

Dave in Houston, I've seen lots of Holley 600's on Chebby 350's that ran like scared cats. Use timgr's formula and see what you get too. (On a carb chart I have a 350 at 5500rpm needs 557 cfm.) Just FWIW.

 

I have a Holley 350 CFM. It is sold by Holley as a direct replacemant for the Mororcraft 2100 2v

 

I called 1-800-416-8628 for Edel's tech assist. They were nice and there wasn't a long hold.

 

I don't think you will ever have to worry about that 304 hitting 7000 RPM unless you have done some serious work to the valve train. Well maybe with 8 blown pistons going down hill very fast in first gear.

As for the 360 carb I run what I think is a 525cfm and it works good on the that motor. With the 304 it was too much carb.

 

A nice 3rd to 1st downshift a highway speeds will take car of that for you, once. :driving:


I'm still trying to tune in my ignition and my MC2100 but that carb runs great, has enough power for what I do, and is pretty good on angles. I know you can find one with a higher CFM rating if you wan a little more than stock. Early mustang guys have a ton of info about these carbs.

Any way 600 cfm seems a little over-carbed for a 304.

 

I also went from a 600cfm 4bbl Holley to a Motorcraft 2100 on my stock 304 and the difference was incredible. It runs perfect, starts perfect, no more obnoxious gas smell from unburnt fuel....and the list goes on......