4bbl running rich.

Part number and picture of the carburetor, too. That would help tremendously. That way we'll know what we're dealing with. If it's a base model 750 vacuum secondary, it does not have an adjustable idle circuit or adjustable air bleeds. Those are damn near mandatory with big camshafts and bigger cubes. It might be good "everywhere else" (doubtful) and be pig rich at idle.