If you have fuel in the air intake hose with fuel shut off valve at bottom of tank open over night, and when running black exhaust, either your brass floats are not sealed and fuel logged or most likely either the needle valve under the float has dirt in it not allowing it to seat or the needle valve is bad or not seating properly; they used to use brass needle valves, I tend to like the rubber tipped ones that seal better or the float setting is off not allowing it to close the needle valve when fuel reaches proper level in the carb thus dumping excess fuel into the carb. You got good advice from DaninOhio on the ignition and that it could be a fuel delivery problem. I have a 1957 420C and a 1959 430C, 2 cyl GM blocks. I have removed a piece of branch out of the 430c fuel tank that was used to check the amount of fuel in the tank by someone and was dropped in by accident. Also check to see if you're fuel bowl has water in it, and if you don't have an inline fuel filter; put one on, it will save you trouble down the road! The only things I bave to add to the ignition side is that I had extra Accel copper plug wires lying around from used on a 68 Camaro and thought they might help get some stronger spark to my AC Delco plugs on my 6 volt system and they did! Always replace the rubber distributor cap seal which fits into the bottom of the cap and make sure you have that felt in the center of your distributor shaft under the rotor and drop 3 to 4 drops of oil into the felt if dry and 1-2 every year.
