The manifold heat riser is a weighted flapper in one exhaust manifold. It is supposed to open when the bimetal spring absorbs enough heat, to allow free flow of exhaust gasses. If the spring breaks or the valve sticks in a closed or partially closed position, you will get low power and poor economy. Short of surgical removal of the balky part, you can wire it or weld it in the open position.
Vikki 1969 Goldenrod Yellow / black 400 convertible numbers matching
