New Edlebrock carb wont idle below 1,000 - Team Camaro Tech
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Troubleshooting Diagnosing problems done here.

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  #1  
Old Dec 17th, 08, 07:24 PM
Bucco47 Bucco47 is offline
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Default New Edlebrock carb wont idle below 1,000

I just dropped in a rebuilt 327 with a very mild cam (intake: 204; exhaust: 214 @ 050 lift). I put a new performer intake and new Edlebrock 1406 carb (600 cfm w/elec choke). It fires right up, no problem, but after the choke kicks off, I can't adjust the idle below approx 1,000 rpm (no tach, I'm guessing). Any attempt to drop idle with adjustment screw and it dies, not sputter and die, just dies like someone cut the key off. It totally appears to be a vacuum leak to me (and the Edlebrock tech on the phone) but i can't find any leaks. All holes on the carb and manifold are used or plugged.... I double triple checked this. While idling (high of couse) I'm reading 16 vacuum on the vac adv port on carb and 21 at the manifold vac port on carb. I've adjusted timing and mixture screws but no luck.

Also, new ProComp distributor, new MSD wires, new Accell super coil (orig canister style), new AC Delco plugs, new AC Delco mechanical fuel pump.

When i set everything up I initially had the distributor 180 out and made half a dozen fained attempts to start it. These attempts caused several backfires through the carb. I know these units don't have power valves but could I have screwed something up with the backfires? Two times included actual "fire" in the carb momentarilly. I also flooded the cylinders and had to dry the plugs before it would fire up. (just giving some background).

What am I missing? Could the stock fuel pump be pushing too much gas? I really don't think it's the carb, but maybe it is?

thanks for any ideas
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Last edited by Bucco47; Dec 17th, 08 at 07:56 PM.
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  #2  
Old Dec 18th, 08, 03:07 AM
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Default Re: New Edlebrock carb wont idle below 1,000

Performer manifold is a spreadbore design, aka, Quadrajet pattern.
Edelbrock carb is square bore design, aka, Holley pattern.

You should install the adapter plate. Something like this one:

http://store.summitracing.com/partde...5&autoview=sku
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Old Dec 18th, 08, 03:59 AM
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Default Re: New Edlebrock carb wont idle below 1,000

Loose the edelbrock....holley street avenger 650, straight out of the box, much better carb..(just an opinion)...how did you get the carb to bolt to that intake?? spay some carb cleaner around the intake gasket and carb mounting gasket while the engine is running, if the engine picks up you know you have a vacc leak..
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Old Dec 18th, 08, 08:54 AM
dnult dnult is offline
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Default Re: New Edlebrock carb wont idle below 1,000

Everett has a good point. I wonder if the secondary butterflies are getting hung up on the manifold and sticking open - creating a vacuum leak in effect.

Timing and vacuum leaks are prime culprets. With vacuume advance active, your idle timing should be hanging around 20*. It is possible the timing is too retarded and that your mechanical advance is kicking in to compensate at the higher RPMs. Drop the RPMS, and the mechanical advance retards until the engine will no longer run.

Put a timing light on it to see where you are at 1000 RPM and start reducing the idle speed. Watch the timing to see what happens.

Check your carberator base gaskets for witness marks indicating a good seal. My holley had an interferance problem with my Edelbrock intake. The accellerator pump lever was hitting the intake causing a poor seal on the base gasket. A 3/8" phenolic spacer took care of that.
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Old Dec 18th, 08, 07:04 PM
Bucco47 Bucco47 is offline
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Default Re: New Edlebrock carb wont idle below 1,000

Thanks for the replies.

I just exchanged the carb with a new one. (the guy i deal with at Advance is awesome)

no change

I had this exact set up on my last 69 with 327 and it fired up right out of the box with no issues.

The 1406 carb is a direct bolt on to the 2101 manifold according to the Edelbrock tech. No adapter required. It appears to seal correctly to the manifold/gasket supplied with the carb. I smothered the air horn with my hands, per the tech's request, and it stumbled and died , indicating no vacuum leak.

I will check the timing as I adjust the idle screw like you suggested Dave. Maybe the distributor is bad. I may put the old points dist to remove the new distributor from the equation.

Can anything internally cause this behavior? Cam/timming chain not installed correctly? bad gaskets, intake, head?
I am going to put a fuel pressure gauge on tomorrow (have to borrow one) and check that, but i pinched the fuel hose as suggested by the tech to see if it ran better (indicating too much pressure from pump) but nothing changed, except when i finally pinched it closed and it starved and died. I pinched it with vise grips at different intervals, tighter each time, with no change.

I'm out of ideas.
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Old Dec 18th, 08, 07:21 PM
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Default Re: New Edlebrock carb wont idle below 1,000

Fast idle rpm adjustment too high?
Fast idle cam not falling out of place after choke is open?
Secondary plates barely open? I would want them open 0.002"-0.004" just to keep them from getting stuck closed.
Idle mixture orifices plugged? Oh wait, new carb.

With 20" of vacuum, and steady, no vacuum leaks hopefully, idle mixture screws DO have a reaction, I suspect a minute leak. I have a 1/8" dia copper tubing for a vacuum gauge with compression fittings at both ends. One end was 1/4 turn short of being tight. After tightening it, engine gained 1" of vacuum to 20" and idle rpm lowered by 200 to 800 curb, (EFI on truck).
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Old Dec 19th, 08, 10:28 AM
67CamaroRS/SS 67CamaroRS/SS is offline
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Default Re: New Edlebrock carb wont idle below 1,000

When I was having my issues with my Q-Jet, I ran an Edelbrock Thunder 650 on a Performer RPM Q-Jet manifold. He rear of the flange is larger to accomodate the Q-Jet so the secondary butterflies getting stuck on the manifold can't happen. The Performer is made to run either a spreadbore or a squarebore. No need to run an adapter. The problem you are having sounds like a vacuum leak. Hold your hand over the primary bore and see if the engine bogs or stalls. If not, then the engine is getting air from somewhere else. As far as the backfires, the Edelbrocks are pretty tough when it comes to that.

On a side note, I HIGHLY, AND I MEAN HIGHLY, suggest making the switch to a Q-Jet. For the street they can't be beat, hands down. They are the best carb for the street and possibly ever built. With the right mods, they can outperform any carb built. They are great for MPG and also when the right mods are done, they can deliver some OUTSTANDING POWER!!! I made the switch about 2 months ago and I kick myself for not doing it sooner. Mine runs like fuel injection.
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Old Dec 19th, 08, 12:14 PM
.Bad75. .Bad75. is offline
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Default Re: New Edlebrock carb wont idle below 1,000

Quote:
Originally Posted by SPARKY69 View Post
Loose the edelbrock....holley street avenger 650, straight out of the box, much better carb..(just an opinion)...how did you get the carb to bolt to that intake?? spay some carb cleaner around the intake gasket and carb mounting gasket while the engine is running, if the engine picks up you know you have a vacc leak..
Ditto this. I had my eddy going to a wiend spreadbore intake and I had a vaccum leak under the carb. Check there first, or decide to go with the street avenger, I replaced my eddy with the street avenger, im not looking back.
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Old Dec 19th, 08, 02:53 PM
Bucco47 Bucco47 is offline
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Default Re: New Edlebrock carb wont idle below 1,000

i just checked the timming while I backed out the curb idle screw to drop the idle and the timing retarded slowly as I backed out the adjustment screw, like a couple degrees a half turn. Is this normal? I turned the dizzy to increase the timimg back where it was as I backed out the idle screw compensating for the retardation but the car eventually died again as I approached an idle below 1000 rpm.
The Edelbrock tech told me to check the fuel pressure to the carb, and it is a bit high, "8". The carb calls for a max of 6.5. It's a brand new stock AC Delco pump. Could this be causing the problem?
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Old Dec 19th, 08, 07:40 PM
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Default Re: New Edlebrock carb wont idle below 1,000

Maybe the rotor springs are too light, need stiffer ones.
Not enough initial timing.
I don't think fuel pressure is the problem.

I have an Edel 1405 on a MCSS Torker manifold atop a 307 V8 and it will idle down to 500 rpm with fulltime vacuum from the manifold, so it can be done.
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Old Dec 19th, 08, 08:11 PM
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Default Re: New Edlebrock carb wont idle below 1,000

Did u check for a vaccum leak under the carburator base? I know for a fact I had a leak on mine with the eddy to a spread bore. Is your choke plate open?
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Old Dec 19th, 08, 08:29 PM
Bucco47 Bucco47 is offline
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Default Re: New Edlebrock carb wont idle below 1,000

Yes, I checked for leaks around the base. It also passed the "hand over the air horn" test. It stumbles and dies when i smother the air horn with my hand so there can't be a leak or it would have continued to run drawing air from the leak.

After the electric choke kicks off, the choke plate remains wide open (I'm assuming you are refering to the butterfly on the top of the air horn).

How can i make sure I am not off by one gear on the distributor install? This is the only thing i am not 100% confident about. I dropped it in with the rotor pointed at #1 cylinder with it at TDC. I don't understand how you can be off one gear since the cam gears on the distributor shaft are not independent of the oil pump slot at the bottom of the shaft.
How can I ensure my distributor is installed correctly?
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Old Dec 19th, 08, 09:01 PM
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Default Re: New Edlebrock carb wont idle below 1,000

FWIW I recently went through a similar problem. My situation consisted of Rochester carb, thin gasket, TV bracket plate, thin gasket, intake manifold. No apparent vacuum leak fairly steady vacuum but on the lower than should be side. Lowest Idle RPM at 1000+. Experimented by removing the TV bracket plate and used a single thick gasket. Problem discovered and resolved.
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Old Dec 20th, 08, 01:22 PM
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Default Re: New Edlebrock carb wont idle below 1,000

Quote:
Originally Posted by Bucco47 View Post
Yes, I checked for leaks around the base. It also passed the "hand over the air horn" test. It stumbles and dies when i smother the air horn with my hand so there can't be a leak or it would have continued to run drawing air from the leak.
There may be a small enough leak and it can't provide enough air to keepengine running.

Quote:
After the electric choke kicks off, the choke plate remains wide open (I'm assuming you are refering to the butterfly on the top of the air horn).
Yes, the butterfly/choke plate may be open fully, but there is a length of linkage going down the the throttle shaft and positions a fast idle cam to keep the carb throttle open allowing the engine to idle at 1400-1600 rpm when engine is cold. If fast idle cam is sticky about its shaft, it may be stuck and carb is 'on' the fast idle cam.

Quote:
How can i make sure I am not off by one gear on the distributor install? This is the only thing i am not 100% confident about. I dropped it in with the rotor pointed at #1 cylinder with it at TDC. I don't understand how you can be off one gear since the cam gears on the distributor shaft are not independent of the oil pump slot at the bottom of the shaft.
How can I ensure my distributor is installed correctly?
Typically, the vacuum cannister nipple will point to #4 or #6 cylinder. If turning the dist body counterclockwise to advance initial timing and cannister hits coil bracket, then dist needs to be repositioned 2-3 teeth clockwise. I suspect as you've done, turn engine over by hand and felt compression stroke on your finger in the #1 plug hole and aligned the timing marks, then dropped in the dist with rotor to #1 port and turned dist body with #1 plug wire marked from cap. Usually, #1 & #8 dist cap terminals are parallel with the front/rear of the engine block. Final adjustment is set by timing light and/or vacuum gauge to highest reading, maybe. Too much initial and it will kick back against the starter and break the nose - but you haven't got this far yet so don't worry about it. Each engine/camshaft/carb set-up is different than the one down the street.
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Old Dec 21st, 08, 01:31 PM
Bucco47 Bucco47 is offline
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Default Re: New Edlebrock carb wont idle below 1,000

Problem solved!

Chock up another bad experience with a ProComp distributor. I pulled it out and put in the old nasty original points dizzy and she idles like a champ.

What a pain in the a$$ !!!

I took a chance with a cheap distributor and crapped out. Live and learn.

Thanks everyone for spending your time helping me out!
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