86 GP 305 4bbl Carb Problem

Rich as in "why is this thing making black smoke even after it's warmed up and the choke is fully open?"

Suspect the canister control valve. (you should be able to figure out where it is by consulting the underhood emissions/vacuum diagram label) Black plastic valve that hangs just above the alternator bracket,

4 rubber hoses attached, two large, one medium and one small. Disconnect them all and plug them with whatever will fit snuggly (golf tee, bic pen cap, 3/8" bolt, etc.) See if the rich condition is improved.

What happens is; the internal diaphram cracks or tears, raw gasoline is pulled from the bowl vent hose thru the cracked diaphram into the signal hose which is connected to manifold vacuum. Very common problem 20 odd years ago.