fuel dribble through primary venturis

[johnt365]

Hi,

Hi all, I'm hoping someone can help me with an idle problem. I have Cliff's book and rebuilt the carb several years ago and tuned to what I thought was perfection.  The car sits most of its life and I noticed recently that it is very rich at Idle on my AFR gauge. 

I can turn the mixture screws all the way in and the idle speed screw is all the way out.  when I do this, I can see fuel dribbling out the primary venturi and its at about 1k.

I thought by turning the speed screw all the way out it would rule out an over exposed transition slot. Maybe this is not a good troubleshooting process.

I thought the needle and seat and/or float might be bad, attached image shows the fuel level after a short drive.

Also the cavity that the book shows should be for idle bypass air looks to be plugged with epoxy so not sure if that means this model doesn't have bypass air.

Thanks for any help.

John
17058204 on a Chevy 350 with a comp XE268H cam.

[Kenth]

I would start with removing the lead plugs to restore idle bypass air.
The clip on inlet needle should be hung from behind on float arm, as it sits now it may bind the needle preventing it from closing properly.
And it looks like the accelerator pump cup has swollen stuck in the bore.

Lead plugs are a sign of commersial rebuilt unit and who knows what more has been done to the carb?

[johnt365]

This carb was rebuilt with a kit and recipe from Cliff about 10 years ago and was running great.  Accelerator pump is Viton and working well. 

The problem is fuel has started to drip even thought all throttle plates are closed. This morning I noticed the top of the float is still wet. Not sure if a new float would be wet on top overnight.

Now I am thinking needle seat and float, but I dont know how that fuel is being pulled through the Venturi  when the throttle is closed. The fuel level in the bowl doesn't seem excessively high to me.

[quadrajam]

Check to see if throttle plates are actually closing fully.
Maybe the fast idle cam is hanggy uppy.
Put a screwdriver in the end of the secondary throttle shaft and turn it CCW
firmly to force fully closed...??

QJ

[Cliff Ruggles]

Install the clip on the needle correctly as mentioned, they can bind up installed as you have it causing flooding issues.  Clean up the carb while it's apart and drive the lead plugs out of the bypass holes in the voids.

Check float height and put it back together with a new top gasket and start the testing over again.......

[johnt365]

Thank you for all the ideas.  Turns out when I reinstalled the carb after an intake gasket repair, I did not check the throttle cable connection. It was about an 1/8 in too short and was causing too much transition slot to be exposed.

I adjusted the throttle cable properly and replaced the 10 yo nitro float and the idle was back and the mixture was much better.

A couple APT adjustments and car runs great again. 

Thanks again!