Lightning boy,
From what I've heard, their purpose was to direct part of the airflow to try to alleviate a lean or rich condition due to a flow characteristic of the particular manifold that carb was used with. I don't know how true that is though, probably Cliff is the only one that would be privy to any of the reasons why the factory would have done such a thing.
I'd like to know that myself as I've got one or maybe 2 of those air valve plates, as well as a couple of the secondary baffle plates with the additional piece welded to them for what I'm guessing is the same reason.
Rick
