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1964 choke tube/manifold question


AD8

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I have read with great interest the replies to my various questions as my project unfolds. Last weekend I chased many old threads relating to heat stoves, automatic chokes and related topics and have learned much along the way. However; I have one question that was not directly answered.

I received the car with a home repair on the choke tube. The tube rusted and broke (assumed) leaving a nipple protruding from the manifold about 1" or so long (see photo). The former owner fabricated an elbow out of tubing with a larger inside diameter to slip over the remaining original tube leading to the choke and the nipple sticking out of the exhaust manifold. He made the joints with aluminum HVAC tape. Not the best but it was holding when I took delivery and the choke functioned, though the repair joints leaked and the choke was pretty dirty.

I took a stiff wire, smaller than the choke tube ID, and inserted it it into the broken nipple. I expected to bottom out on the inside wall of the manifold, opposite the point of entry but was only allowed a couple inches before the wire was stopped.

The exhuast heats the air in the choke tube which is drawn into the choke by vacuum and relaxes the coil, slowly closing the choke. The question: Is the tube from the manifold simply an open route from inside the manifold up to the choke? It doesn't make sense that the engineers would design raw exhaust up the pipe to foul the choke. That's the question I could never answer. What is the original function of the automatic choke; how is it supposed to work? What is indide the manifold? There must have been a way that air is heated without drawing exhaust with it. I know, probably simple but I couldn't find the answer in the manuals and had to ask.

Thanks,

Jim

BCA 43102

post-44854-143142894358_thumb.jpg

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Your tube in the manifold goes all the way through and is intended to have clean air (you are missing the other end of the tube route) that is picked up from the corner of the carb under the air filter housing.

Inside the manifold tube there is a thin metal strip twisted along its length...it must slow the air flow so air is heated when it goes to the choke coil. there should be insulation on that tube going to the coil as well.

Ted

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Maybe this link will help:

http://www.thecarburetorshop.com/Automaticchokes.htm

Ted added the information about the tube which passes through the exhaust. The exhaust heats fresh air. If the tube gets a hole (generally after about 30 or so years), raw exhaust can enter the tube through the hole and then enter the choke where it causes all kinds of problems.

Jon.

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There is a simple way to test if the stove pipe is OK. With the engine running use your hand to feel for any hot exhaust blowing out of that tube............there should not be any. You may not be able to poke wire through the tube as it likely has a bend in it, just blow some air through to check that it is open. In your photo I can see what appears to be the end of the stove pipe which has about an inch of the broken pipe to the manifold sticking out of it, soak it with penetrating oil and after a day or so gently wriggle the broken pipe and it will likely come out. You may be able to find a replacement pipe from some of the parts suppliers but any steel pipe of the correct diameter will do, just shape it around the back of the head and up to the choke, and it must be covered in insulation to keep the heat inside.

Automatic chokes are nothing to be afraid of as they are very simple but a lot of people struggle to maintain and adjust them. Park your car outside in cold weather and early in the morning touch the accelerator pedal (without starting the engine) to activate the choke then turn the adjustment so that the choke butterfly only just closes without any tension on it..........simple. Don't take much notice of the graduation marks on the housing.

Koala

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WC65, Carbking, Koala -

Thank you for your input. I have have the choke tube and insulation for the assembly. It was removed at the repair (described earlier) to show what remained of the tube at the manifold. I suppose my question has been answered and can best be described as a "tube in a tube" inside the manifold. The inner supplying heat while the outer prevents exaust from being sent to the choke. Using Koala's technique I should be able to tell if damage has occured within the manifold, though carbon inside the choke indicates it is so. If I am able to loosen and remove the remaining tube from the manifold, are the replacement choke tube assemblies, such as offered by CARS, complete? Mostly concerned with restoring the function within the manifold. I have seen other varieties of aftermarket universal heat stoves that attach externally to the manifold but would rather return original design.

Thanks to all and a Merry Christmas!

Jim

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