I could use a 1974 slant six manifold heat control valve expert!

"Boomy" sounds like you've got a big exhaust leak. Which gaskets (brand) did you use when assembling and installing the manifolds?

Ceramic coating on the spring is not good. That's a bimetallic strip wound into a spiral. It wants to be naked metal in order to function properly.

With the engine cold, grasp the counterweight and rotate it anticlockwise (as viewed from the front). It should turn easily, but there should be noticeable spring tension. When you let go, it should promptly spring back clockwise until it hits a hard stop. The total amount of rotation from one extreme to the other is roughly 90°.

With the engine hot, do not grasp the counterweight without a heatproof glove or something, or you'll burn yourself. But everything should work the same as described for a cold engine, except the spring tension should be less.

That valve is there for a good reason and unless you're building a race car, removing/defeating it is all drawback, no benefit.