Jim,
If you grab the top of the distributor, you should be able to rotate it maybe 10 or 15 degrees. It will spring back to position. If you look on the right hand side of the distributor at the block, you will see a silver (depending upon how clean your engine is) looking thingy with an arm that connects to the distributor. You will see this arm move when you rotate the distributor. If you start the engine and reach over and goose the throttle at the carb, you will see the distributor instantly jump. Thats your vacuum advance working. If you hold the throttle open you will see the distributor rotate and steady out. That's your centrifiugal advance.
The whole idea here is that the engine needs to have the spark happen at different times depending upon if you are accelerating or at what RPM the engine is turning. "Advancing" the spark means it is happening sooner relative to TDC.
I'm certainly not an expert on this, and others can give you a more detailed explanation, but that's the basic idea.
If you are in doubt about the vacuum advance, you can remove it, and suck on a tube attached to the vacuum port. If you have no resistance, it is shot. If you can create enough of a vacuum, it will move.
Hey,
Hope you will consider coming to the upcoming Southern Bolter Gathering. Might even be some Duke fans there. (my wife)
Kurt
