Hi all, and thanks for the ideas. I am pretty overworked just now, and I haven't had much time to wrench. Tomorrow I head off on a longer working trip, so the fuel in the truck will get another month to fester.
I would guess that Floyd's ideas are not so far off, but the carb was rebuilt 5 years ago, and I should hope a carb rebuild would last longer than that. I am aware of the problems with the Rochester, and it has always had a little hiccup when accelerating, but lately it has been much better, no hesitation at all.
Yesterday I had a chance to pull the plugs, and they were well filled with carbon. Also the rotor seems a little worn. A tune-up is in the works. But not today. It still seems strange that it suddenly went from working great to working like horse-manure. And I still suspect that the fuel in the bottom of the tank has separated or otherwise gone bad. In any event, the solution will have to wait a few weeks.
Thanks for the help.
Karl