Thread: carb. question

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i have a 330hp. 350 gm crate motor (i bought the long block) and put a edelbrock performer air gap intake on it withe a 1 inch carb spacer and a 600cfm edelbrock preformer carb. my problem is that the motor is running rich at idle. i've adjusted the mixture screws to lean it out at idle but it still has a rich odor. i bought a 600cfm carb cause i thought that i could jet it up for power, never thought it would be to fat at idle? anyone got any suggestions.

600 CFM shouldn't be a problem on that motor. Is the spacer a 4-hole or open plenum? In fact, with the air gap, why a spacer? Have you checked your float levels? A stuck or dirty needle and seat can cause real problems.

A thought - call Edelbrock's tech line.

its a open plenum spacer. i have read alot about them in chevy high performance and they did a biuld on the same motor with the same intake but with a 750 holley and praised the benifit of the spacer. if the floats were the problem would if still be ok on light and heavy acceleration?

if the floats were the problem would if still be ok on light and heavy acceleration?

Very likely. Idle is a separate circuit, and doesn't supply very much fuel. A float set too high could be dumping enough fuel to mess up the idle, but not enough to hurt under acceleration.

Chevy Hi-Performance notwithstanding, I don't see the value of an open plenum spacer on that particular Edelbrock manifold. Edelbrock designed it as a "two-holer" for a reason. It's a dual-plane design, making it work efficiently at street-driven RPMs. As a contrast, the Victor Jr. is a single plane design, also for a particular reason - high RPM operation.

Mixing the open plenum spacer with a 180 degree, single-plane manifold may not be the cause of your rich idle, but I can't see where it would give you more performance.

Agree with Henry on the open plenum spacer.

Never assume that calibrations and settings are correct right out of the box for a new carb. New does not mean absolute!

Richard set me straight on setting up my # 1406 Edel. Precise
reset cleaned up all problems. Hope this helps.

i guess i'll pull the spacer off this weekend and try setting my idle mixture from scratch. hey henry how do i check the float hight on that carb do you know what it should be? i'm a body guy still learning the tuning and mech. ins and outs thanks

Here's your homework assignment:

http://www.telusplanet.net/public/gi...delbrock_1.htm

I hope the information on my site (mentioned above) is helpful to your members. Two quick comments regarding the problem identified.

First Edelbrock carbs are very susceptible to high fuel pressures. Make sure to keep the fuel pressure below 5 psi, volume is much more important that pressure.

Secondly it does really depend on your total engine configuration, but in general you will find better drivability with a 4 hole spacer on any dual plane manifold. An open spacer concentrates the intake revision and associated turbulence right at the carb base which can effect mixture distribution, velocity, and proper flow.
Whereas a 4 hole spacer maintains the airflow integrity. I would definitely try removing the spacer and seeing if there is a noticeable change.

Volvord 784VC
http://www.telusplanet.net/public/gilesij/Volvord/

if homework were like this when i was younger i'd be mo book smarter'r . volvord 784vc awsome iste thanks again to those who have helped. i'll be tuning this weekend . anyone know of any worthwhile books on tunning and performance info, i read alot of automotive lit. but sometimes the books i buy are alittle disappointing. i appreciate the help

I run a 600 cfm edlebrock performer carb with my performer
manifold,I have been running these for about 18 years my
350 is 240 hp the carb has been very good all these years
i only rebuilt it once because of dirt in carb. when i first put
the carb on i used a spacer on my 327 i threw the spacer
away when i installed my 350 because the spacer would
not seal and it created a vaccum leak. there is no difference
in performance with or without spacer.

its only been rebuilt 1 time that was about 3 months
ago.

Originally posted by DennyW
Yes, I understand what you mean, but, check this out. A confined area, pressure, or vac, uses the confined space as a whole. I'm not disputing you, but this also works.

Hey denny what kind / name of manifold is that ? I think it looks like a 180 deg manifold with an air gap cast into it.

I've got the same problem with a blown motor runing 2 Edelbrock 600's, the idle fuel screws do absolutely nothing. I run them all the way in and the engine keeps on idling like I did nothing. Also the plugs are very black. I talked with an engine builder, he says these carbs are jetted/needled fat. I would look at the plugs after a run down the freeway/ track, hee hee, to see how they look. You might be to darn rich for the idle circuit to do anything. Just food for thought.

If you can't get the idle screws to change the idle, then your throttle plate is possibly open to much. This would mean that you are idling on the primary circuit. You may need to adjust the timing to bring the idle up and then close the throttle plates before you can adjust the idle mixture. You may need to go to a large jet also.