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85Sierra 05-09-2005 06:17 PM

600cfm not enough?
 
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

NAIRB 05-09-2005 06:39 PM

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

Max Keith 05-09-2005 07:48 PM

600 CFM not enough?
 
That 600 will feed your engine plenty of fuel and air way past 5500 RPM.

stepside454 05-09-2005 07:51 PM

I think Id personally use a 670 Holley for that application.just my 2 cents

85Sierra 05-09-2005 08:05 PM

I dont want to spend a ton of money, my 406 cost me 3600ish and that is alot when your 19 and you have a g/f and insurance and what not

what i would like to know is what does everybody recommend?

600 edelbrock
600 holley

lluciano77 05-09-2005 08:21 PM

The idle circuit on a 600 CFM carb may be too lean. You will definetely loose some top end at 600 CFMs. How much is hard to say. I don't think you would loose any throttle response going at least 650.

Max Keith 05-09-2005 08:27 PM

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.

Hippie 05-09-2005 08:31 PM

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.

Tech @ BG 05-10-2005 07:27 AM

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.

85Sierra 05-10-2005 07:57 AM

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

85Sierra 05-10-2005 08:02 AM

using a cfm calculator it says i need about 650 will a 600 be insufficient?

Tech @ BG 05-10-2005 08:05 AM

Quote:

Originally Posted by 85Sierra
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?

spinn 05-10-2005 08:24 AM

Quote:

Originally Posted by NAIRB
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.

Hippie 05-10-2005 10:20 AM

Quote:

Originally Posted by 85Sierra
using a cfm calculator it says i need about 650 will a 600 be insufficient?

You must have plugged in 100% volumetric efficiency, 80% for a street motor will probably be more like it and that's optimistic. Using 80% it comes out to a 517 cfm.

85Sierra 05-10-2005 06:02 PM

speedpro flat tops 9.7:1ish
crower , 278 462/470
performer Rpm
stock heads, 76cc, 3 angle valve job
stock stall but if i get it rebuilt i will step up to a 2400


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