Idle issues

[ksurfer2]

This weekend, I removed the choke plates on the dual eddy 1407's that I have on my 512 with indy 440-25 intake. Now the idle is extremely high....about 3000rpm. I have the idle screws back all the way out and the idle mixture screws closed all the way. The carb linkage is ok and the throttle is fully closed at idle. The front carb is "dribbling" a significant amount of fuel out of both primaries. No visible fuel coming from the rear carb. Fuel pressure is 5.5psi. I took the front carb off, disassembled and cleaned it. Reinstalled and still have the same issue. Any suggestions as to what is going on?

 

[ksurfer2]

Things I have tried:

1. removed and cleaned the needles and seats...no change
2. Swapped the tops of the carbs....no change
3. Swapped the primary venturies from both carbs....no change (same issue with the front carb even with the venturies from the back carb in it, and no change in the back carb either)

 

[dvw]

When you pulled the chokes did you get all the remaining linkage correct? Are the springs on the rear throttle shafts holding the blades shut. Sometimes they need an additional wrap. If the linkage is correct and not holding the blades open, you most likely have a vacuum leak. Intake gasket, Intake top, carb adapter(s), carb base(s), missing vacuum plug. In the past I had one other issue that caused the same result. 1407 carbs. The rear throttle blade screws on one carb loosened maybe 1/32 of a turn. The blades would then slip and get stuck in the bores.
Doug

 

[Fran Blacker]

Crack in fuel bowl a remote possibility, seen it once. Sounds more like what dvw saying.

 

[493 Mike]

The high idle speed is causing fuel flow in the main circuits. Slow down the idle/fix the problem and the main circuit will stop flowing.
Mike

 

[ksurfer2]

I think I found the issue....I had the carbs sitting on half inch spacers so the throttle linkage would clear the manifold on the rear carb. This put the carbs very close to the underside of the scoop. I found I could still get the linkage to clear the manifold by removing the half in spacer, but stacking 3 gaskets under the manifold. I only did this on the rear carb. Since the throttle linkage cleared the manifold on the front carb, I only used 1 gasket there. What I failed to notice is the "cam" for the pump squirter was hitting the manifold keeping it from closing all the way at idle. I put 2 more gaskets under the carb and the pump squirter appears to be closing all the way. In the interest of keeping peace with my neighbors, I won't be starting the car at 8:30 on a Sunday night to test. I will fire it up tomorrow after work, but I think this will fix the issue. Stay tuned....

 

[dvw]

Assuming your 440-25 has the 1/2" anti revestion plates? I believe I trimmed the lower part of the throttle arms when I ran the 1407's on mine. Only ran 1 thin gasket on each.
Doug

 

[ksurfer2]

Well, adding the additional gasket under the carb did raise it enough to allow the pump squirter to close all the way. However, that did not solve the issue. When running, I could feel a lot of air being sucked through the front carb by holding my hand a couple inches over the front carb. There was no air that I could feel being pulled through the rear carb. I pulled the carb off and found the screws holding one of the primary throttle blades were VERY loose allowing a significant amount of wiggle. I tightened those up and the blade now appears to be closing properly. Once again it was too late to start the car without pissing off the neighbors, so we'll see tonight if that solves the issue. I may have really dodged a bullet here. Those two screws were dangerously close to backing all the way out and would likely have done catastrophic damage had they been ingested by the engine.

 

[dvw]

Well, adding the additional gasket under the carb did raise it enough to allow the pump squirter to close all the way. However, that did not solve the issue. When running, I could feel a lot of air being sucked through the front carb by holding my hand a couple inches over the front carb. There was no air that I could feel being pulled through the rear carb. I pulled the carb off and found the screws holding one of the primary throttle blades were VERY loose allowing a significant amount of wiggle. I tightened those up and the blade now appears to be closing properly. Once again it was too late to start the car without pissing off the neighbors, so we'll see tonight if that solves the issue. I may have really dodged a bullet here. Those two screws were dangerously close to backing all the way out and would likely have done catastrophic damage had they been ingested by the engine.

I chased this issue for awhile with mine. Intermetantly it would have 3000 rpm idle. Glad you found it. I added a little locktite to the screws. Funny my 1407's are over 30 years old. Only the secondary screws on one carb ever came loose. None of the others. You can see where i trimmed the bottom of the carb throttle arms.
Doug

 

[BSB67]

……..I had one other issue that caused the same result. 1407 carbs. The rear throttle blade screws on one carb loosened maybe 1/32 of a turn. The blades would then slip and get stuck in the bores.
Doug

Wow. Good call Doug. I Would not have guessed it. I’ll need to store this one away in the memory bank

 

[ksurfer2]

Tightening the throttle blade screws fixed the issue. It is amazing how those two tiny screws, just a bit loose, could completely screw up the proper operation of the carb.