If you have a Rochester carburetor (and the likelihood is very high that you do), the super-rich running will be from a stuck power piston. There are lots of articles about that here (many I've written). When the piston fails it sticks in the "down" position and this leaves the power valve open (a simple spring-loaded ball) allowing a lot more fuel to enter the manifold. Time will never fix this...you have to disassemble and clean very well.
If you're fortunate enough to have a Carter carburetor, the super-rich condition will be from a failed diaphragm (accelerator pump diaphragm some will call it). If it has failed, vacuum will suck gas straight out of the float bowl and in to the manifold. I've written about that too, but we're not currently adding to tech tips so it won't be there.
Please let me know if you want me to resurrect any of the old carburetor articles for you.
