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Vacuum line routing to choke on carter carb


jw1955buick
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Finally started this 322 I bought after it was dormant for eight years, choke wasn’t working then I noticed the missing screw on line on the backside of the choke, what does this look like and where should it come from? Take a very careful look at these pictures and also tell me if anything is missing or wrong looking in a mechanical way 

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There is only one vacuum line on that carb, and that's the rubber line going to the distributor. The line to the choke is a hot air tube that is supposed to come from the exhaust manifold on the passenger side, usually right above the thermostatic flapper valve. 

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The choke stove pipe. It's a rigid line that has a flare and nut on the carb/choke end. There should be an insulated sleeve over it to retain heat . It runs behind the rear of the valve cover/head then turns back forward to slip into a little tube on the back side of your exhaust manifold (green line approximates routing behind the head and manifold in first photo). It pulls outside air through that tube in the back of the manifold where it warms as the manifold heats up from the exhaust gasses, then up through the stove pipe and into the choke housing where it heats the thermostatic spring and will gradually open the choke valve during a cold weather start. You can buy replacement kits from most of the regular parts suppliers Bobs, CARS, etc., that have a tube and insulator sleeve.

engine 2.jpg

exhaust manifold pass.jpg

Edited by vindictive (see edit history)
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Tension from the thermostatic spring under the black cover should hold the choke butterfly closed when cold. The screws that hold that cover can be loosened and the cap rotated to increase or decrease the tension. Those bi-metal springs hold up pretty well, but replacements are available for pretty cheap if needed.  If you don't have a factory service manual, get one. It is pretty thorough on the carb, and choke operation and set-up. Check out the Hometown Buick site as well, they have a lot of the manuals/literature available to view online.

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6 minutes ago, vindictive said:

Tension from the thermostatic spring under the black cover should hold the choke butterfly closed when cold. The screws that hold that cover can be loosened and the cap rotated to increase or decrease the tension. Those bi-metal springs hold up pretty well, but replacements are available for pretty cheap if needed.  If you don't have a factory service manual, get one. It is pretty thorough on the carb, and choke operation and set-up. Check out the Hometown Buick site as well, they have a lot of the manuals/literature available to view online.

Good info.  But don't adjust the choke until you have a  functioning choke stove pipe...otherwise the choke will never open.

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You can also buy a standard Edelbrock/Carter AFB electric choke, flip the spring and install it like the heat pipe choke. I think there is even a listing on ebay that has this swap already done and should be a bolt on retrofit. 

 

The hot air choke will only work properly if the butterfly and counterweight are free to spin on the exhaust manifold, and the thermostatic spring that tensions it is in good working order. If this piece is stuck in the open position or it is missing the spring, then it will not allow proper heat circulation between the intake and exhaust manifolds to properly operate the choke. How fast it opens also depends on your ambient weather local to you (people in Texas will have an easier time than people in Wisconsin). I have tried several times to get mine to work and I have never got it to open and close properly, even with replacing the old choke spring with a new one. I live in Washington state and used to drive my car in 10*F weather conditions. The electric choke has never left me stranded, but the old heat pipe has (in terms of having to pop the hood and manually hold it open/closed).

 

In my latest configuration, I bought a pre-formed brake line roughly the same size as my old hot air choke tube, cut the end off one side and affixed the proper fitting for the choke housing. I then crimped and sealed the end of the tube with a vacuum cap that dangles back behind the engine. It is retained with a cheap metal tube holder off of the back of the block in one of the empty head bolts and it looks stock, you cannot tell its a fake unless you sit on top of the air cleaner.

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  • 2 weeks later...

The nut usually used on a choke like that looks very much like the one in your pic. I'm not sure if it is right, because of that ferrule sitting next to it, but it LOOKS right.

 

The nut is slid on the tube, and then the tube is flared (or maybe double flared if it is a steel tube). Then, the flare goes right up against the seat on the choke, and the nut holds it in place. No ferrule.

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