Baffle In L-134 Manifold

Stock L-134 manifold has a baffle/butterfly plate in it. Originally I *think* there was some sort of mechanism on the outside of the manifold that allowed this baffle to open up once a certain temperature was obtained? Something along the lines of a spring and a counterweight? Regardless, mine is long gone and after chasing down just about every other source of exhaust noise and causes for horrible rich condition, I may have finally narrowed it down to this baffle being more or less stuck shut? Can anyone confirm how this is supposed to operate, and whether the notch on the end of the protruding shaft is clocked with the baffle itself (ie if the slot is horizontal, the baffle is shut, vertical it's open)? Thanks!!

 

Check this out: http://www.1945gpw.com/c-12-G503_WWII_Jeep_Exhaust_Heat_Control_Valve_detailed.aspx