Another vote for a defective power valve.
The Rochester to a 1947 is aftermarket.
The correct original and (opinion) far superior carburetor would be a Carter W-1 tag number 574s.
While it is very easy to throw rocks (deservedly) at the Rochester; a rich running issue may also be created by a defective fuel delivery system. That carburetor shouldn't see more than maybe 3 psi. Virtually no electric fuel pump may be used without some method of reducing the pressure. Also, there are some new fuel pumps that produce way to much pressure.
Check your fuel pressure with a pressure gauge before going into the carburetor. If the carburetor were truly "professionally rebuilt", then it should last a few thousand miles without issues.
Jerry must be in a good mood today; normally he would tell you the primary use of the Rochester B is an anchor for a catfish trot line !
I cannot really agree with him as that would be water pollution. A better use is a doorstop !
Jon
