Weird problem with 3269S carb on my 62

[Anthony P.]

I am having a weird problem on my 3269S (BK1) carburetor that is on an aluminum 340Hp manifold.

1. The linkage is free and no binding.
2. If I run the engine, even for 5+ minutes the linkage starts to bind partially open and it will stick at the same exact location every time. It is definitely at the carb since I eliminated the rest of the linkage.
3. I can manually bring it back to idle by pulling on the linkage.
4. The first thing I though of was the that the linkage was binding from heat warping the carb base.
5. Here is the weird part. If I get the linkage to bind and I shut the engine off, the linkage moves back to the idle position immediately and moves nice and smoothly with no binding.
6. If I start the engine. I can get it to bind, and again shutting the engine down it returns to idle. This will repeat over and over.

Given that there is only a few seconds between repeating 6 above, the carb definitely is not cooling down enough to free the linkage.

For some reason it it seems like vacuum is holding the the throttle blades open even though I have no idea how this could happen.


I am going to remove the carb Sunday, but my 1st thought is that the base gasket is somehow getting caught on the throttle plates, but just a wild guess.

Any thoughts on this?

Otherwise the car runs great, but I do not like this cruise control feature

Thanks,

Tony

[Timothy B.]

Re: Weird problem with 3269S carb on my 62

Tony,

I think your correct in checking the simple things first like the gasket but I bet that's not the problem.

My first thought is the throttle shaft is bushed and the clearance is closed by heat and the expansion of the aluminum base and bushing around the throttle shaft. AFB's have good clearance in this area exactly for this reason.

Second thoughts are that the throttle shaft is wore or slightly bent or throttle blades need to be fitted better in there bores. When the engine stops, air past the throttle blade stops and the spring pulls the blades closed a bit further to idle engine.

[Anthony P.]

Re: Weird problem with 3269S carb on my 62

The binding is definitely heat related. I pulled the carb and can not see anyplace where things are rubbing, but then it is such a slight bind it does not surprise me.

What just confuses me the most is that I only feel that bind when the engine is running (hot), however, if I "immediately" shut it off, everything moves freely. There is no way things cooled off that much in 2 seconds. I just would not expect the vacuum to make it feel like that.

I looked at the throttle plates and eyeballing them, they appear to be centered in each of the bores.

Since this is such a slight bind, should I remove the shaft that the throttle blades are attached to and lightly rub it down with emery cloth?

Thoughts?

Thanks,

Tony

[Gary B.]

Re: Weird problem with 3269S carb on my 62

What about going with a stronger return spring??
And paint it the proper colour.

[Anthony P.]

Re: Weird problem with 3269S carb on my 62

I actually thought about that, but would like to fix the problem, since the wife will be driving the vette. I am just concerned that it could get worst and really stick at a higher speed.


What I temporarily did was to slightly shorten the spring so it pulled harder. That did help, but, I still can get the bind at times, however, with a quick hit of the accelerator it does go back to idle..

[Timothy B.]

Re: Weird problem with 3269S carb on my 62

Tony,

If you think you can remove the small screws that hold the blades without breaking them then it's not a hard job to clean the shaft some and refit the blades.

The screws are brass and are punched to prevent them from backing out so you may need to file the other side of the screw flat with the shaft before turning with a screwdriver. Be careful here.

[Anthony P.]

Re: Weird problem with 3269S carb on my 62

Thanks Timothy,

Since I will need to file those screws, I take it I will need to find some new ones, correct? I am looking at the main suppliers and have not found them yet.

When I re-install the screws, can I just use a center punch and something behind it to support the head, to lock them back in place? ( have not done any carb rebuilds except for easy holley ones)

Tony