Are you talking about the exhaust manifold flapper valve? Actually located in the exhaust manifold below the intake manifold.

Yes

It probably needs a new spring. The spring keeps tension on the valve and when the motor starts up and is running, the heat from the exhaust passing thru heats up the spring causing it to expand and gradually open up the "flapper". Here in Fla it is not needed so I eliminate that system.
The official name of this devise is "heat riser"
https://www.hemmings.com/blog/article/all-rise/
Hemmings article explains its function.
Another article-
https://forums.aaca.org/topic/133165-the-heat-riser-valve-really-important-or-really-not-important/

I believe that there should be a bi-metallic coil (like a choke control) to control the flapper valve there, with a small conventional spring to try to keep it from rattling too much. Are you having running issues, or just curious as to what the spring/coil assembly does?

I am having running issues. Runs okay when it is cold, but when it warms up it shuts off and idles rough. I have had points, condenser, carbs all looked at. Is this my issue? Would it cause a compression leak?

Hudsonly,

jarrod

[b]Make sure the flapper valve is free to move. You could have a bad Condenser or coil that opens when it gets hot. I've had NOS and NORS condensers pass on a condenser tester but fail when installed on a car. I've been told that new chinese ignition parts are junk to start with. [/b]

I agree with Ed -- the condenser is a definite possible suspect. But I mentioned running issues because I just rebuilt my engine and, in reassembly, went from a 1 bbl to a 2 bbl manifold, and I immediately had problems -- low power, bad idle, bogging, all worse when hot. I finally noticed that my bi-metallic coil was working properly (expanding and contracting in response to heat) and my spring was in place to keep it from rattling, but the hook that goes around the flapper shaft that the coil is on was corroded and grinding against the coil. In my case, this meant that the spring was preventing the shaft from turning, so instead of the coil turning the shaft and opening the flapper valve, the valve was sticking shut and the end of the coil was just pulling itself off of the post that stops it, creating a bad exhaust restriction -- and the bogging and lack of power. This may well not be your problem, but it's easy to check for -- when the engine is cold, look at the coil; the outside of the coil has a little hook that should be sitting against a post. Once the engine is fully warmed up, check again -- the end of the coil should still be sitting against the post, but the coil should be a slightly different diameter. I fixed my problem by running safety wire around the coil flap and securing it to the post so that the coil had no choice but to open the valve when it moved in response to heat. Has been working fine ever since.

Hi, thanks for the responses. The bimetallic spring in the exhaust rattles and I think that may be the issue. Condensers are cheap to buy so I’ll get a new one as well.

Hudsonly,

Jarrod

Just to clarify things, I mean Ignition Coil, not the coiled spring.