Running Rich

What cam is in it? what carb is it and what is the stock jetting and does it have power valves? Did it back fire on startup or was it running bad at all before this problem? In your first post you mentioned pinging, that doesnt sound like a rich condition. How much compression is on the engine? Does the distributor have a curve in it or is it locked out? Toatl timing varies from car to car but I would start in the 36 degree total range depending on compression and fuel type available.