The Stovebolt Site Forums The Shop Area Engine Shop air through choke control?

Hey guys, quick question: Can the carb suck air through the manual choke control cover?

In playing with the Carter YF 3211 carb on the Blue Funk's '57 235, which has been sucking air on acceleration, I noticed the plastic cover was loose. When I pushed the cover against the carb, the engine idle improved. I tightened down one of the machine screws holding the cover to the carb, and replaced another, which also held the bracket for the choke control cable, as it would not tighten down.

The engine now accelerates more smoothly. I haven't taken the Blue Funk out for a test drive as of yet, as it is still dark outside and I've got other things to do, but was wondering if I hadn't resolved a problem.

Thanks.

One can bush choke/throttle shafts.

Ed

Sounds like your carb has been converted from an auto choke to manual. The round plastic cover did not come on manual choke models. Yes vacuum can leak from there. There is a gasket that goes under the cover. It needs to seal good.
George

It's intended to draw HOT air through a piece of steel tubing from a passageway near the exhaust manifold. That's needed to make an automatic choke release. It sounds like you've got some sort of Rube Goldberg manual choke conversion on an auto choke carb. That's a calibrated air leak that's built into an auto choke system.
Jerry

Yes, the choke is a converted one! Thanks for the info, Wrenchbender!

If, by "Rube Goldberg", you mean "Davey Do rigged", you've got it right, Jerry!

This is the same carb you located and sent to me a few years back, Jerry. I believe you had informed me at the time that an automatic choke is much more efficient than a manual one. Would I listen to you? Nooooooooooo!

Silly me.
.
There is a port near the choke mechanism where I assume the the piece of steel tubing went that I plugged off. When you say "a calibrated air leak that's built into an auto choke system", are you saying that this leak could be sucking air?

I do believe I need to follow your past words of wisdom and convert back to the original automatic choke system.

"Any takers on talking Developmentally Delayed Davey Do through this?"' he humbly enquired.

Do you mean, Ed, like, put a rubber washer thingy on the shaft so air isn't sucked?

If you really want to keep the manual choke:

Remove the airhorn from the bowl.
Locate the vacuum passage that controls the choke which begins in the throttle body and continues up through the bowl.
Find a fisherman
Beg from the fisherman a small split shot lead sinker about 1/4 larger in diameter than the vacuum passage in the bowl.
Carefully, using a small punch and hammer, insert the lead into the passage (the lead is soft and may be removed, if desired, at a later date).
Reassemble the carburetor.
Fabricate a small metal tag punched with the words "choke passage mod" and place it under one of the airhorn screws.

The exact same mod could be made where the passage continues from the throttle body to the bowl, rather than the bowl/airhorn if desired.

Jon.

My father had a saying "An automatic choke is smarter than all drivers, and most mechanics!" He was a man of great wisdom, and I miss him every day. Converting back to an auto choke is a pretty simple project unless someone has done some modifying to the lever arm that moves the choke flap back and forth. Carb King should be able to provide the proper choke cover for your carb, and whatever attaching hardware might be missing. Then it's simply a matter of unplugging the port you blocked off and installing a "choke stove"- - - -a sheet metal item that clamps onto one of the exhaust manifold runners and a piece of steel tubing (brake line works) to connect the choke stove to the carburetor port. Universal-fit choke stoves are available on Ebay for very reasonable prices. Then the carb draws a small volume of air through the tube and provides clean hot air (not exhaust gas) to the choke assembly to make the bimetal spring in the choke to relax and allow the choke flap to open as the engine warms up. That "vacuum leak" you're experiencing is actually a small controlled airflow through the carburetor that shouldn't affect the ability to make idle mixture adjustments or make the engine run rough.
Jerry

Davey Do,

Throttle shaft bush is for replacing worn shaft/bore by drilling a larger hole in the carb body, making and inserting a suitably made bushing to fit the shaft/bore. Probably not a drill press operation, find someone with a milling machine.

Ed