Adjust 1972 Bronco Carb 302

[Ark Bigfoot]

I have a 1972 Bronco with 302 V8. I rebuilt the carb. Now it starts easy but after about 30-60 seconds it dies. The butterfly is open when this happens and when I close it to about 1/8 inch it continues to run without stopping but if I open it up ii dies. I have the adj screws at 2 turns. Also there are two tubes coming out of the manifold. The top one goes in to the carb with a hex nut holding it. The bottom one goes to the top plate of the carb connected with hose. . I am saying this because the last tube broke off at the manifold. Don't know if this is causing my issues or not and how can I fix it?

 

[jckkys]

When you say butterfly, are you talking about the choke plate or the throttle plates? A '72 would have a Motorcaft 2100 carburetor stock. Is that what you have? The vacuum tree behind the carb has a hex drive top and pipe thread screwed into the intake. Is that the tube or one of the tubes you're referring to? Any vacuum fitting in the intake that breaks off would be a huge vacuum leak that can't be ignored.

 

[Ark Bigfoot]

Pictures

Here are some pictures:

One shows the carb butterfly which I have to close to 1/8" to keep running. It starts easy but after 30 secs starts to slow down then dies. One shows where the metal line about the size of a pencil broke off the manifold. One shows where the broke like attaches to the carb plate nipple. One shows where the top manifold line attaches to the choke. I have the choke set at about 3 clicks counter clock wise from the center.

 

[Ark Bigfoot]

https://postimg.cc/gallery/cCdPMSH

 

[DirtDonk]

Maybe I'm doing something wrong, but I can only view one image. It shows the exhaust manifold and heat-riser tube (it's the image with your hand holding an open end wrench)

When the engine dies from the choke opening up, is it at idle only, or does it die no matter what you try to do with the throttle lever? In other words, even at higher rpm it will still die?

Paul

 

[jckkys]

It would have been helpful if you specified that you were talking about the exhaust manifold. These are the tubes you need;https://missourimustang.com/choke-heat-riser-tubes/The choke plate isn't what keeps the engine running it's the fast idle cam linked to the choke plate. This keeps the throttle open for cold starts. It sound like your engine won't idle without the choke holding the throttle open. The set up instructions that came with the rebuilding kit will tell you how to set both the idle mixture and idle speed. Do these with the engine at operating temperature ie. warmed up.

 

[jckkys]

The Missouri Mustang sight didn't work so try CJ.https://www.cjponyparts.com/classic...m_term=1101201851884&utm_content=All Products

 

[Ark Bigfoot]

I have it running okay now. Drove it about 100 ft. Brakes are out. I was 19 years old and there was a noise coming from the engine. The guy at the "red neck garage" said I needed an rebuilt engine put in it although it only had 95,000 miles. I had him put one in. He used I think a Mustang 302. How do I find out what year the engine is. I am trying to find the correct Tube Choke Tube which will fit. Also how hard is it to put in? It looks like it is forced into the exhaust manifold. No fittingsl. Just a hole. Thanks fellows for your help and expertiese in getting this running.

 

[Ark Bigfoot]

https://i.postimg.cc/FKDWD2pN/IMG-2667-1.jpg This is the Tube-Choke-Tube which came off the exhause manifold and connects to the carburetor nipple with a hose. It is the lower one on the exhaust maniflold.

 

[DirtDonk]

And they might have used (and probably did) the original manifolds from the Bronco, so that's what you'd be looking for, or something similar.

While you're waiting for parts, in case it's going to be awhile before getting the right ones, if your old ones are broken off completely or at least have holes in them, you can cap off the ends at the carburetor and drive around like that no problem. Especially as the weather gets warmer.

The smooth tube-looking one at the rear of the air-horn of the carb is not an actual vacuum leak, but it can allow dirt into the intake, so can be plugged off with a vacuum cap or bit of hose with a screw stuck into the end.

The threaded one at the back of the choke housing however, is a vacuum leak (although just a tiny one) so you can thread on a brass cap that can be found at most hardware or auto parts stores.

If the new parts are available and will be there soon, the extra trouble of capping the holes temporarily is probably not worth the trouble. But if it's going to be awhile, it's worth doing.

Paul

 

[Ark Bigfoot]

Thanks DirtDonk. I will see if I can find it. Am in no hurry. How hard is it to install?

 

[1970 Palmer]

The two choke heat tubes can be easily replicated from a piece of 1/4" galvanized steel tube available at any local auto parts store. You would also need a new 1/4' brass compression ferrule available at any hardware store. Reuse the brass threaded compression coupler nut, and the asbestos looking insulation tubing. With a tubing cutter, a tubing bender and five minutes you can fabricate a nice looking, fully functionable repair. It might not be a 100 point concourse part like the $35 kit, but it will work just fine.

Note, as Paul alluded, BOTH tubes are very important. The insulated tube provides heat to operated the choke thermostatic spring. The second tube is the "clean filtered air" supply to the heat tube. Without the clean air supply, the choke will eventually stop working as it gets full of sucking dirt.

 

[DirtDonk]

Good point. Even on simple old utility vehicles, everything is part of the system.

And I have no idea how easy/hard it is to get the old rusty stuff out Ark. Never had to do it myself. Been pretty lucky in that regard, and now that mine is finally in need, I have headers and EFI instead.
That's one way to get around it!

Paul

 

[davebb]

choke heat

Many exhaust manifolds that provide choke heat have a tube inside of them that the exhaust gas heats. Air is sucked through into the choke housing from the nipple on the air horn of the carb through the exhaust manifold. I've seen many choke housings filled with crud from the exhaust because this tube inside the exhaust manifold is rusted away allowing exhaust gasses into the choke housing. I've capped off the air horn nipple and holes in the exhaust manifold then used an electric choke heater and stopped the little vacuum passage in the housing from being a vacuum leak to make the system work.

 

[jckkys]

Here's a good description of how to rebuild the heat stove in the exhaust manifold.https://www.428cobrajet.org/sites/default/files/choke-stove-rebuild.pdf. This applied to 428 CJ manifolds, but the parts are the same.

 

[jckkys]

This is the part the tube is pressed into. https://www.428cobrajet.org/sites/default/files/choke-stove-rebuild.pdf

 

[davebb]

Here's a good description of how to rebuild the heat stove in the exhaust manifold.https://www.428cobrajet.org/sites/default/files/choke-stove-rebuild.pdf. This applied to 428 CJ manifolds, but the parts are the same.

Wow. Very nice! I guess that type manifold won't let exhaust gas into the choke even when it's all nasty in there. Some do.