Check the power valve piston in the carburetor. It's probably stuck in the down position which is bypassing the main jet with a severely over-rich mixture. All the symptoms you're describing are characteristic of a VERY rich mixture. Rochesters are notorious for sticky power valve vacuum pistons.
Jerry
Just finished rebuilding my "B" last night and the power piston is the one thing I'm not quite satisfied with.
The large part of the piston moves in its bore pretty well. The travel against the little check ball in the well housing is what I'm not sure about. If I move the piston against it's spring all the way...the small end tends to hang on the housing rather than float freely back against the check ball and small spring. But, I might be moving it farther than what occurs in "real life." As long as the small end stays somewhat engaged against the ball...and doesn't completely leave the housing...things move OK.
That's probably a terrible explanation....but if anyone can interpret, do I need to remedy that?
