Idle Too High

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Boogercj7

Boogercj7

Mopar Boot
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I have a stock 318 with a Holley Street Dominator Intake and an Edelbrock 600 CFM carb. I can't get this thing to idle below 850 RPM unless I advance the timing alot. Any suggestions to get the idle down some??
 
I only wish I could get mine to idle under 1000 rpm - 1200 rpm for that matter.......
 
Retarding the timing is NOT the answer, even though it will lower the idle speed

Finding the REAL problem is the answer

Is this a new carb, or did you buy it used? Some guys "with big cams" used to drill holes in the throttle plates to try and help a big cam idle better --get the butterflies back down into the transfer slots

Either you have something hanging up -- like the butterflies can't close, or a vacuum leak.
 
start the engine and while it is running, spray wd-40 around the intake ports, carb base, and any other vacuum areas of the intake and carb. If it speeds up, you may have found your leak.

Check for any stray open vacuum lines.
 
67Dart273 said:
Retarding the timing is NOT the answer, even though it will lower the idle speed

Finding the REAL problem is the answer

Is this a new carb, or did you buy it used? Some guys "with big cams" used to drill holes in the throttle plates to try and help a big cam idle better --get the butterflies back down into the transfer slots

Either you have something hanging up -- like the butterflies can't close, or a vacuum leak.
Click to expand...
X2. Check the linkage that opens the secondarys if it's bent or binding, sometimes the throttle plates won't close all the way. You may want to pull the carb off so you can see if all the throttle plates close and there are no bent ones or extra holes drilled.
 
67Dart273 said:
Retarding the timing is NOT the answer, even though it will lower the idle speed

Finding the REAL problem is the answer

Is this a new carb, or did you buy it used? Some guys "with big cams" used to drill holes in the throttle plates to try and help a big cam idle better --get the butterflies back down into the transfer slots

Either you have something hanging up -- like the butterflies can't close, or a vacuum leak.
Click to expand...

It's part of the solution if he has it advanced. Reread the original post. Seems he was telling him to retard it from what he had done to it. Have you tried turning the idle screws in till it stumbles and then turned them back out till it picks back up a little. Is the air cleaner in place? Don't imagine you have a choke pull off with a dominator intake. What's the plugs look like? Lean?
 
I got the carb used. I checked the throttle plates and they are closing all the way and there are no holes drilled in any of the butterflies. I also checked for vacuum leaks by spraying carb cleaner all around the base of the carb, the throttle shafts and the vacuum lines. No leaks that I could find. It will not adjust down with the air cleaner in place or removed. I tried adjusting the timing until I got the highest vacuum, but it was way advanced. So for now I have the timing set at 10 degrees BTDC. It seems to run fine at that setting, except for the high idle. By the way, the cold idle adjustment screw is not even touching the very first step on the fast idle cam.
 
Vacuum leak --- somewhere. Might be right at the ports, or a crack (defect) in the manifold, you run a brake booster? What ports you have plugged / in use? Did you try plugging the PCV? Unhook and plug the brake booster port? Gotta be somewhere. There is no carb in the world, that if the butterflies close, the car will still run, much less idle high.

THAT INTAKE MANIFOLD is a spread bore, correct? What did you do to insure sealing around the carb base? What spacer/ adapter/ gaskets did you use?

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PHOTOS WE WANT PHOTOS,

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67Dart273, I think you may have something there. I used a spread bore gasket between the intake and a 1/2" phenolic spread bore spacer and a spread bore gasket between the spacer and the carb. I do have power brakes. I have not tried to remove the PCV and power brake lines and see if it makes a difference. I will try that this weekend and I may even get a spread bore/square bore adapter if needed.
 
Have you verified the throttle return spring is pulling all the way against the idle screw?
 
67Dart273 said:
I'd bet money this is the problem

If you can find one of these --notice the price-- it should solve the problem. Intall at the carb end of things

http://www.jegs.com/i/Edelbrock/350/2732/10002/-1
Click to expand...

After I read your post, I looked at the exact same thing and I noticed the price and said,Dang, I should just get one of those and try. I will be checking the PCV and brake booster lines this weekend and more than likely ordering one of these plates.
 
Ok, plugged the vacuum ports for the PCV and the brake booster, no luck. Installed the recommended adapter, still no joy. Any other suggestions?? I didn't have this problem with the Holley that was on there before. I changed the Holley out because the throttle shaft was worn out and leaking and I got a hell of a deal on this Eddy. I am about ready to order me an Eddy air gap intake to see if this will solve my problems.
 
Can you post a photo of the bottom and top of the butterflies? Turn the idle screw clear out so the primaries are closed, and look carefully for any gaps.

At this point, I donnoooo.......

You say "the Holley didn't" so this would suggest a specific problem right in that carb, OR a base vacuum leak, one or the other.
 
something wrong between carb and engine, if idle screw not turned in too far. Last 3 Eddys we used would idle at 500, if you could stand the fumes-that takes a rod/jet kit. Look elsewhere first; what is the vacuum? what is initial? Is the vac gauge jumping around?

Set timing to highest vacuum, then screw in idle screws, to get the best, then lower curb idle. If the idle screws are more than 2 turns out- leak beneath the throttle plate( keep in mind, the throttle plates just just be barely open, like .010 max.) .

Once carb good, now your total advance is too much, but that initial/carb setting is what it wants; now limit total.
 
Next chance I get, I am going to remove the carb and check the throttle plate closing. I pretty much just bolted this thing on after removing the top cover to make sure there was no junk in the bowls. Right now the idle screw is out all the way and the throttle plate cam is not even touching the idle screw.
 
Finally got some time off from work and had some time to mess with this thing. I had my suspicions that this carb had been messed with by the previous owner when I discovered the choke linkage was not installed correctly. So I pulled the carb off today and sure enough, the throttle plates were not closing all the way. After disconnecting all of the linkages to make sure they were not the culprit, I removed the throttle plates just to make sure the shaft would in fact move further in the closed position. When I removed the throttle plates, I noticed that one of the screws was different from the others. This confirmed that the previous owner had in fact messed with this carb. So when I went to put the throttle plates back in, I installed them so they would be closed as much as possible. Then I shined a flashlight from the top of the carb to see just how much they closed and they closed a lot better than they did before. Reinstalled the carb and now I can actually dial in my idle using the idle adjustment screw. Thanks for all of the help.
 
I had the same issue, because I had replaced the base and gaskets of the carburetor/intake with thicker versions so because it was taller the throttle cable was throwing the idle off. Stupid mistake that I overlooked. Thank guys for the clear insight always turns out to be some thing small and simple.
 
krazykuda said:
start the engine and while it is running, spray wd-40 around the intake ports, carb base, and any other vacuum areas of the intake and carb. If it speeds up, you may have found your leak.

Check for any stray open vacuum lines.
Click to expand...

WD 40 leaves a nasty residue on everything , I like brake clean spray better for vacuum leaks:blob:
 
GEO said:
WD 40 leaves a nasty residue on everything , I like brake clean spray better for vacuum leaks:blob:
Click to expand...

Whatever works.

Some sprays increase the idle, others decrease it when you look for vacuum leaks....


However, notice how old this thread is.... #-o
 
Yeah, haha
Just leaving more info for when new people come looking for same issues .

Always good to update
 
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