[JJR]

I had the same bolt problem, it is fairly common. I would develope an exhaust leak from the gasket between the intake and exhaust manifolds. The threads for the small bolt were stripped. You could tighten it a little bit but could not tighten it enough. I ended up installing a heli-coil so I could use the current size bolt. As for the flapper valve, mine is siezed in the closed position. I have an extra exhaust manifold with a good flapper valve but the surface where it meets the intake manifold is warped due to rusting.