[rich weyand]

In 1968, the feds mandated AIR pumps, and timing was delayed so the mixture was still burning on its way into the exhaust manifold. Together with the air that was being pumped in, that burned up the extra whatevers and cleaned up the exhaust. Also helped the cats along. Unless you are going back to an AIR pump and 4* BTDC timing and ported vacuum, the cats won't clean that smell up.