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

sounds like your spring is just slippeing off its perch, can you fold that tab over the stop? Cold motor causes the spring to close the flapper, apply heat to the spring with a heat gun/hairdrier. youll see it start to move. That is the direction the force on the spring needs to be contained to move the flapper. As the heat moves the spring, the flapper should move counterclockwise, diverting the exhaust down instead up up to the intake stove. Here is a great vid on what its supposed to look and sound like. Although he is missing the factory bumpstop thingy that makes the valve not tick when it hits its stop. I dont know what material could survive that hot manifold (asbestos pellet?) but it was in a FSM I saw.