What size carb please.

[Blackpony]

I decided to change the stock carb on my car. My question is what size CFM do i need. I was told the current carb is a 600 CFM however i was told that I could go a 650 or even a 700. I will be installing a new Air Gap Edelbrock intake also and the cam in time but not right now. What would be the best to use with a cam being installed later on down the road.

[ibstrokin]

Check this guy out, My dad, uncle, and a few friends have used him with no complaints. He can usually build you a carb for less than a new one costs, that will outperform a new one. But he is on the North side of Dayton.

[Rick93coupe]

I think Brian is talking about Chris's carb shop or something like that.

The formula for figuring the right size carb is

cubic inches x maximum rpm / 3456. This should equal the correct cfm carb.

306 x 6500 / 3456 = 575.52 Atleast thats what I was always told.

[Black Horse]

Yup - that is a good estimator!

[85_SS_302_Coupe]

Stock size is actually 575cfm. A 600 is perfect for a warmed over 302, but if you plan on getting a cam and maybe some budget heads, like GT40s or something, then go with a 650 double pumper. Personally, i wouldn't waste my time on vacuum secondaries. For a stock long block 302 with just an intake, a 600 double pumper will rock...it'll have great throttle response and a great balance between torque and top end. You can't expect a ton of top end with the stock heads, or else a 650 would be better. I wouldn't go bigger than 650 unless you end up getting some nice aluminum heads and a hot cam and run it to 6500rpm.

I bought my 650dp for a .030 over 351 i was supposed to buy from a guy but he backed out so i used it on my stock 302 with a Wieand Stealth intake (far superior to the Air Gap IMO, and way cheaper) and i eventually ran a best of 13.8 with a ton of traction problems..i think it would've at least gone 13.5, maaaybe even 13.20 depending on how well it could hook. Then with ported 351 heads and an X303 i dropped a whole second off my ET to a 12.8, and i'm still destroying the tires off the line. With control arms and slicks i think it'll go 12.20s all day, and that's with a (at the time) box-stock 650dp that i hadn't even jetting yet.

[Blackpony]

Thanks for all the input. Next question i have is which carb would run better a Holley or Edelbrock

[85_SS_302_Coupe]

Thanks for all the input. Next question i have is which carb would run better a Holley or Edelbrock



That's a huge debate right there :lol:


Personally, and this is strictly my personal opinion so take it as you will...Holleys are better for racing and Edels are better for daily drivers. People will say Edels are easier to tune...that's because they have less tuning options. Go to the track and count how many Holleys you see racing vs. how many Edels you see. How many Edels are in professional drag racing? Would Nascar use Edels if they were allowed? I doubt it.

The best thing you can do is educate yourself and make a serious effort to learn how to tune a Holley, and once you get the basics down you won't have any problems. I sawed the choke horn off mine this summer and everyone threw a fit saying it'll never start when it's cold out...but i can fire it up right now with just a few pumps. Jetting a carb is as simple as turning a few screws...you just have to understand what you're doing, what the carb is doing, and WHY you're jetting to get it right, which isn't a big deal. I'd recommend buying at least one good book on Holleys, and they even have an awesome DVD for like $20 that goes over all the basics like setting floats and changing jets and power valves. Hell if you want i can even burn you a copy of it.

[Blackpony]

I had a Holley long ago on a Buick i had and it was never right. It might have been just me but it's hard to say. I know with what ever i buy it'll take some time to tune it in. I might just to be sure take it in and have it adjusted correctly

[Goldenpony]

600 sounds just about right. One of the most common mistakes is to put too big a carb on.

[Greg Seibert]

Here's a little carb discussion for you to ponder.
As you can see, there are other variables to consider besides just using the calculating formula.

http://forums.corral.net/forums/showthread.php?t=868898