3x2 idle problem

[Roger Coen 30751]

I have a newly rebuilt motor. When I took off my carbs to do the motor they worked fine. After I put them back they won't idle when cold. The auto choke seems to be working fine. When it gets to normal temp it idles fine (700-750rpm). If I set the idle when cold then when it gets to normal running temp it idles at 1500 or so. I've checked all fittings and they are hooked up and no vacuum leak that I can see. All 3 carbs were new from Holly 4 mo.ago.

Any ideas? What next?

TIA, Roger

[Michael Hampson]

Re: 3x2 idle problem

Roger,

I have 3x2's also on a new rebuild, and had a similar problem. The choke linkage serves two purposes, the first and most noticeable being that it closes the choke plate when the engine is cold. This aids in starting and runs the engine a little rich by restricting the air a bit. The choke linkage also operates a small cam on the same side of the carb, which opens the throttle plate a little bit also when the engine is cold. The cam, as I recall has several graduations, so that as the engine warms up, the throttle plates close more and more until they rest on the idle screw on the other side of the carb when the engine is warm.

It sounds to me like the small 'tab' that opens the throttle plate needs a little "tweak" to open the throttle plate a little bit more when the choke is set. This may be due to bumping the carb while removing, or perhaps that with the close tolerances of the newly rebuilt engine, it's a little harder to turn when cold than it was.

Anyone else feel free to comment. It's been a few months since I worked on mine.

Thanks, Michael