2100 Carburetor electric choke vacuum leak

[Old2New]

Hi guys, I have a 2100 carburetor on my 1963 F250 with a 292. I did a smoke test on the engine and found that it has a vacuum leak out of a threaded port under the electric choke. When the engine is running I can hear a loud whooshing sound coming from it. I have read mixed views on whether to plug it or leave it open? Some say it's to keep the electric choke from burning up and others say they close it. What should I do? It sounds like a massive vacuum leak but I don't want to burn up my choke. It is threaded and I believe it was the port for the automatic choke tube. Thanks guys

[darrell]

it doesnt matter what you do its just there to draw heat into the choke.

[dmsfrr]

I'd be inclined to close it off, just on general principal if nothing else.

This carb's a 4bbl but is the fitting you're asking about like either one of these?
(in the yellow circles)


Also, here's a link that might help...
http://www.carburetor-parts.com/Chok...it_ep_638.html
.

[Old2New]

Originally Posted by dmsfrr

I'd be inclined to close it off, just on general principal if nothing else.

This carb's a 4bbl but is the fitting you're asking about like either one of these?
(in the yellow circles)


Also, here's a link that might help...
http://www.carburetor-parts.com/Chok...it_ep_638.html
.

Yes like the top one. I know for certain that its for the choke tube. I had a 2150 on my 78 f100 and the 2100 and 2150 are very much alike. I went ahead and plugged it and it actually idles MUCH better now. It was pulling a TON of vacuum before it was plugged. It hurt my finger almost to hold it over the hole. It even idles better now after cruising and coming back down to an idle. It obviously had air flow through it with the choke tube but now its an unfiktered sojrce of air so capped it goes. A manual choke wouldn't have a vacuum there and they have electric chokes put in all the time and they all work fine so I think I'm good. Thanks guys

[dmsfrr]

Great!
You'll probably need to do some carb and maybe even some timing adjustments now.
Glad it's working better.

[darrell]

Sponsored Links (Register now to hide all advertisements)

ive never heard one make a noise or affect the idle

[craig]

Some will argue this, but here's the deal. The vac that you feel is manifold vac that is intended to operate the choke pull off piston, it also does draw the hot air from the choke tube from the ex manifold or ex crossover tube in the intake if it's a Y block. So, if you plug the opposite end of the heat tube, it can't draw vac and if it can't draw vac, then the choke pull off piston won't operate properly if at all. This is why at the end of the choke tube there is a return line to the air filter housing or a tube connection to the air horn at the top of the carb or in the case of a Y block a small round filter at the end of the line on the intake manifold, you don't want it sucking unfiltered air. The original heat tube system was restricted either in the ex manifold or the crossover tube in a Y block so as not to create a major vac leak, but still draw hot air for the choke stat. Take a look at a universal Holley, Edelbrock or Carter AFB and you will see either a rubber hose from the choke to the top of the carb or a compression nut with a screen on the choke outlet. Either way the vac is restricted but still allows the choke pulloff to work properly

[Old2New]

Originally Posted by dmsfrr

Great!
You'll probably need to do some carb and maybe even some timing adjustments now.
Glad it's working better.

Im pretty sure that the carb needs re adjusted no. That nasty vacuum leak sound has gone to. It was real loud. So loud that I could hear it in the cab while driving. Wonder if this could be why my spark plugs were fouking so quickly? Does a vacuum leak do that?

[Ole Don]

A vacuum leak with cause a lean condition. Black soot on the plugs is because of a rich condition. Causes for rich could be float level. With today's fuel, I like to set the float as low as possible so at engine shut off, boiling will not overflow in to the manifold. No mater if it came that way or not, a spacer under the carb to keep it cool will help. As little as 1/2 inch should help.
FWIW: when trying to change choke parts, if you need to plug a small vacuum port, this works. Heat up the soldering iron, and make several little balls of solder in different sizes. Locate the hole to be plugged, set a ball of solder on it and hammer it home.

[cousinjd]

The choke housing also has a plug on the underside of the channel where the pulloff piston moves, about the size of a dime. If this plug is missing,major vac leak. Just some thoughts that might come in handy.

[Old2New]

Originally Posted by cousinjd

The choke housing also has a plug on the underside of the channel where the pulloff piston moves, about the size of a dime. If this plug is missing,major vac leak. Just some thoughts that might come in handy.

Well I'm imbarrased to say that the leak is coming from the missing plug. I was sure that this hole was for the choke but after your comment I double checked and this was the issue. I took the plug off of my 2150 but how do you get the plug to stay there? I put it in and stuck a piece of tape on it to hold it for now.

[craig]

I've seen a glob of JB weld holding them in (put it on the outside so as not to get it on the piston or bore)

[Old2New]

Originally Posted by craig

I've seen a glob of JB weld holding them in (put it on the outside so as not to get it on the piston or bore)

Is there ever a reason to take it off? I could try a small bit of jb weld I guess.

[craig]

you won't need to take it off, it was there to bore the hole when the housing was manufactured

[scicala]

Sometimes when the choke heat tube corrodes through, you get carbon there from the exhaust gas. Removing the plug is about the only way to clean out the piston bore in that case. They are standard size aluminum expansion plugs, so no problem finding new ones if the old one is damaged after removal.

Sal