I have been reading up on Seafoam Motor Treatment and decided to run some through the engine yesterday. But the plugs that I cleaned a couple of days ago were already too dirty to get my motor runnin'.
So I cleaned them once more, warmed up the engine and then I soaked it with Seafoam through the carb. The amount of smoke was much less than I imagined. So possibly the engine wasn't as dirty as I assumed. Or maybe I did not let the Seafoam soak in long enough.
After that, I installed ANOTHER set of new spark plugs, this time AC Delco R43S. We shall see soon if they work any better than the Bosch plugs I had installed.