Fuel/air mixture ratio??

What carburetor? What kind of build on the engine? What ignition system? Any recent changes to the carb or distributor? Is the carb new? Rebuilt? Same for the distributor and engine itself.

You could be running really rich, but you could also have the wrong timing advance or other ignition problem. We need more information.

While a wideband A/F gauge is nice to have, people have been tuning engines for a long time without them. Even if you have one, it only tells you if/when you're rich or lean, not what's causing it.