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

They probably stretched the coiled spring when they sand blasted it, so that spring is probably junk.

We cut those heat riser butterflies out of the manifolds on the engines we do. Once the shaft of the butterfly is removed a person can weld the steel insert sleeves shut with a wirefeed so they don't leak exhaust.

Never liked the thought of those stuck butterflies running half closed blocking the exhaust flow.