[HuggerCST]

I would start by checking the choke pulloff. The diaphram inside has probably gone bad, and is not pulling the choke open after startup, causing a rich condition, and the black smoke. Is this a 4bbl Quadrajet? If so, the pulloff is the small (half dollar size) round thing mounted on the right front of the carb. Vacuum supplied by the rubber hose on the front pulls the choke open slightly untill the engine warms up.