When it cools it coils up, when you start your car, let itidle and then run, clean air from the air cleaner is sent drawn by vacuum thru the the exhaust manifold where it is heated and that heated air uncoils the spring and opens the choke on top of the carb. Problems are: the tubing breaks or comes loose, it fills up with crud or is so mis-adjusted that a cutting torch won't open it enough.
Jim

 

so the spring could just wear out. The gasket around the cover is torn as well, making the cover move. Ever since i got the car, this has been an issue. I also open the butterfly up, by hand, and it didn't open all the way, no matter which way i turned the cover/spring. Then when i hit the throttle, it binded before it shut the butterfly, hence the fact my throttle stuck today.

 

Mine did the same thing. The PO put it up on a lift and crushed the gas line. Enough gas got thru but ran rich, Plus the rubber gas line to the fuel pump wasn't sealed with a clamp.

 

all fuel lines look okey.

 

Installed new choke spring and cover, seems to have fixed it, car runs great. Still need to adjust it alittle, to get it perfect, but all and all seems to have fixed it. Actually drove it last night, and it did not stall!!! No missfireing,no backfires or anything!!!!! The flowmasters through the tri-y's, gives it a great sound. Felt good to get her out, i evan did a one legger!! thanks guys.

 

How do you adjust the air/fule mixture with a vacuum guage?

 

Adjusting the idle (air/fuel) mixture should be done after you have adjusted points, timing and idle speed. The engine should be at normal operating temperature so that the choke is fully open.

Start with the idle mixture screws two full turns out from bottom. Usually at this point, the carb will be running rich (which means too much fuel and/or not enough air).

Start the car and connect a vacuum gauge to any manifold (not timed) vacuum port. Your reading should be steady and somewhere between 15-20 inches. The idea is to adjust the mixture screws to get the highest possible vacuum reading. Since two turns out is usually a little rich, begin by turning one (doesn't matter which one) of the mixture screws in (clockwise) 1/4 to 1/2 turn at a time to lean out the mixture. Take note of the new vacuum measurement - if it is the same or higher than before, turn in another 1/4 to 1/2 a turn and repeat until you notice a drop in vacuum. At that point, turn the screw out (counterclockwise) 1/4 to 1/2 a turn. Keep track of the number of total turns that you make to get to the final setting and make the exact same adjustment to the other mixture screw. This will adjust your carburetor to "lean best idle".

There is a good chance that you will need to re-adjust your idle speed after you set your idle mixture.

Good luck!