Another view of the choke operation. I got a good one and looked at it closely as I never had a mechanical one that ever worked. The choke element itself that bolts into the manifold well is extended when its cold (seems like it would be the opposite, eh  ) Anyway, that springy extended state pushes the choke valve closed and it is with a snap once you press the accelerator once on a cold morning, that snap also moves the fast idle cam up into the throttle lever, kicking it open a little. When the car is started, the well starts to heat up and the spring starts to relax, but it doesnt pull the choke open, the choke itself is under light spring pressure to open itself so the spring only pulls away from the choke rod, the choke spring on the carb body actually pulls itself open. It can only pull itself as fast as the bimetallic spring relaxes, and that is where you tap the gas again , releasing the fast idle cam gravitationally and it drops a notch or 2 setting the idle closer to basline idle. Pretty cool to watch it happen. Same idea with the riser on the manifold. I looked at that thing for a few minutes until I realized the spring only does one function, and that is to raise the diverter into carb heat position. It keeps it there under tension until it gets warm enough and starts to "unwind" and then the exhaust gas flow pushes the diverter back to where it likes it to be, doverting the gas toward the exhaust flange. I was under the impression that the bimetallic springs were more like the ones in a "stove" setting like on the side of a carb. Those are a captive type whereas the spring actually pushes open and pulls a rod through the bimetallic spring heating action to manipulate the . The divorced choke we have and the exhaust riser use an opposing force (main body spring and gas flow) to reset to normal operating temperature. The non operational bi metallinc springs on my friends car both didnt do anything when heated, no movement, or very small weak movement.
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