Hot Rod Forum banner

600cfm not enough?

6K views 49 replies 15 participants last post by  Hippie 
#1 ·
Im having trouble deciding on what carb i want holley/BG/edelbrock but anyways i was wondering if 600cfm is not enough for my motor

406sbc wont see more than 5500
 
#2 ·
You know, you could use a larger carb if you wanted to. However, a small carb is not always a bad way to go. You'll get snappy throttle response and you've got enough air to turn it past 5000 anyway.

Remember that the factory 396-325 horse engine had a 585 Holley from the factory. They ran very well with that carburetor. It's better to err on the small side than the large side.


Brian
 
#7 · (Edited)
what CFM?

Cold hard fact, running too large a carb will hurt you more than running one that is too small. If running too small a carb was going to hurt you, then that makes it hard to explain how NASCAR engines make 700 HP with a 390 4 bbl, and a lot of saturday nite dirt trackers make lots of hi rpm hp with 500 Holley 2 bbls, with out frying the engines.
 
#8 ·
My old 383 SBC had an Erson TQ30 cam, Weiand Xcelerator single plane, Vette dual point, 1-5/8" headers, TH400 and 3.73 posi and resided in a '72 Chevelle SS. I ran a 4776 600 DP on it with the primaries leaned out 2 or 3 jet sizes. The thing would pull a house and rev to 6000 no sweat and pulled an honest to God 17 MPG on the highway. Not bad since according to conventional wisdom I had the "wrong" carb, intake, distributor, cam, torque converter and headers. I never got it to the strip but I sold the motor to a friend. Installed "as is" in his '71 Monte Carlo with a TH350 and 3.73 posi it ran 16.0's all day long through full exhaust on Sears all season radials with that same carb. The Sears tires didn't hook until about halfway through 2nd gear. Now you're probably saying "16.0's.... Big deal, that ain't fast!" No but considering what it was in and the exhaust and tires I don't think it's too darn bad. He installed Nitrous on it later on and took me for a ride, when it finally hooked in 2nd gear and the speedometer came back off the peg we were going 85 MPH. The only change he made to the carb was to rejet it. You can doubt me if you want but that's my story and I'm stickin' to it. You'll be fine with a 600.
 
#9 ·
To make an accurate carburetor recommendation we're going to need some more specific information about your combination. What it is, and how you're going to use it. I know it can be tough especially when you're young, and just getting started, but you are going to be much better off waiting a little longer and getting the proper piece, then having to purchase another one in the future. Carburetors work on air velocity, so a smaller carburetor will generally run richer on the same combination, than a larger one will. If you have to go one direction or the other the smaller carburetor is a better choice.
 
#12 ·
85Sierra said:
406
cam,intake,pistons,head work,headers/duals,

now the motor wont see more than 5500 and its going into a 3600lb g-body stock rear end with 273's for now (have 9" with 350 gears) and a th350

all street driven and maybe make a few passes this year
What kind of parts are you using? How much compression, what type of heads, and intake are you using? What is the stall speed on your torque converter?
 
#13 ·
NAIRB said:
You know, you could use a larger carb if you wanted to. However, a small carb is not always a bad way to go. You'll get snappy throttle response and you've got enough air to turn it past 5000 anyway.

Remember that the factory 396-325 horse engine had a 585 Holley from the factory. They ran very well with that carburetor. It's better to err on the small side than the large side.



Brian
yep,i put a 600 on my 440 an started it. ran rich, but hey its not gonna be the end. BG's got the fix, to give your fuel a place to mix.
 
#22 ·
85Sierra said:
well at the moment i have a 750 q-jet that is totally rebuilt and works perfect but in the future i would like to upgrade but im looking into the thunder avs 650 or the speed demon 650 and i cant decide
Why didn't you tell us you had a Q-Jet in the first place? I wouldn't consider switching an "upgrade", get Doug Roe's book and spend some time on the Q-Jet, it probably works "OK" right now but you still have a way to go to be perfect. Once you get it "perfect" the only thing better on the street is EFI. It doesn't have the visual appeal of other carbs but it sure does work and once you've experienced one properly dialed in you'll start thinking it looks pretty good after all. Just my $.02 but from what I've seen in other posts there are quite a few experienced rodders here that feel the same way.
 
#23 ·
Carb Upgrade

I tend to agree with Hippie on this. Stick with the Q-jet and get to know how it works. Other than them not being the most eye appealing carb on the market, theres not a thing wrong with them, and they have just as much potential as any other carb out there. Save your bucks for something later on that will give you more bang for the buck, than another carburetor.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top