Not all are adjustable.
>With the engine off and cold, you slap the throttle with what you think will get the engine to start. This also sets the fast idle cam.
>As soon as the engine starts the Vacuum choke pull-off cracks the choke open, so it won't flood. Then you slap the throttle again, which drops the idle-speed.
As the engine warms up, the bi-metal spring unwinds and opens the choke. About three minutes later, depending on the ambient temp, the chokevwill be wide open, then you can slap the throttle one more time, to disengage the fast-idle cam.
The choke mechanism sets in a pocket on the intake. Underneath that pocket is a hot-air chamber, that crosses over from the exhaust ports of one side if the engine, to the other. In one exhaust manifold is flapper valve, that forces some to most of the exhaust gasses to travel thru that X-over, to do two things; 1) to heat up the carb to prevent icing, and 2) to cause that bi-metal spring to unwind. After the engine has been running for a bit, that flapper also unwinds, no longer forcing hot gasses thru the X-over.
>As often happens with time, that X-over plugs up with cooked-oil. and the gasses can no longer pass under the carb. This also prevents that Bi-metal choke-spring from unwinding, and then the choke does not come off. and when the ambient temp is hovering just below zero with high humidity, icing can occur, which is extremely frustrating.
Therefore
before trying to adjust that straight link-rod choke, you gotta make sure; 1) that the bi-metal spring is still working and 2) that the carb heating system is still open, and that the flapper-valve is still functioning. Also, 3) if the air-filter housing has a heated air intake, that too has to be inspected.
If you have a later-model car that was born with a constant-temperature air-cleaner, and if you run it with that system defeated, you will have A/F ratio troubles, as the ambient temperatures get colder.
Some to most of these cars also had various ignition timing controls added to deal with that heated-air system. Bandaids galore.
If this type of car is running headers, there is no flapper valve, to help the carb. If you install a 4bbl on it, without heated air, in Missouri, in the winter, you are just asking for trouble. maybe more like begging, lol.
All that said
The Bi-spring can usually be rotated on it's pivot, to add or subtract tension, which will change the time it takes to unwind. and
the choke pull-off opening can be adjusted by bending the loop in the linkrod. and
the fast-idle can be adjusted with the fast-idle screw. and
the vacuum to the pull-off can be delayed by a restrictor in the line.
Correct operation also depends on factors like Idle-timing, Throttle-opening, valve lash, vacuum leaks, and general tune.
