Mystery manifold part

[Eric Goforth]

Hello,
I got my '66 C10 running last weekend and drove it around a little. It has a straight six, I believe it's a 250. When it's cold it seems to start right up with full choke. After it's warmed up it runs kind of erratically. It will start to die. If I pump the gas pedal I can keep it running, but it has very little power.

After it's died I checked the clear inline fuel filter that I installed when I replaced the fuel pump and it's almost full of gas. The previous owner told me that he rebuilt the carburetor. It's obvious that he did do this because the carb is pretty much spotless, so it must have been soaked in carb cleaner, etc. He seemed pretty knowlegable about the truck, so I'm thinking that he probably did an okay job. I'm wondering if I still might have a blockage in the carb somewhere? It's pretty strange though if as abruptly as the really rough running, bucking etc. started it will seem to clear up.

Once when it was (barely) idling in the parking lot of an autoparts store I noticed that there was a piece, it looks like some kind of valve, that was moving on its own. This part was attached to a clockspring, or maybe a bimetallic switch. Does anyone know what this piece is? I'm guessing that it's something to allow the exhaust manifold to heat the mixture for cold starts. As this piece was tilting back and forth the idle would go up and down, sort of like a second throttle. Is the top manifold the intake and the bottom the exhaust?

The choke is on top of the carburetor, it is manually operated. I can see it open and close when I push/pull the choke control on the dash. Below that is the throttle I can see it open and close when I push the throttle linkage back and forth. This is below that on what appears to be the collector for the exhaust manifold. I can turn this "thing" back and forth by hand. I can't see it moving maybe if I had another hand to hold the mirror, flashlight, hold the throttle open, and move this "thing" back and forth.

The thing has a clockspring looking thing that seems to shut it (maybe a bi-metallic strip), I think that it's designed to heat the incoming charge in cold weather. Any idea what this thing is, how it's supposed to work, in what position I should try to lock it, if I can't get it to operate normally?

Thanks,
Eric