And check the centrifigal advance curve springs* Try pulling the weights - the springs should hold it back - but you can pull them apart. It may need lube.

*If this applies to your distributer.

 

Great comments. Just to clarify the vacum at idle bit: The carb has an opening on the upside of the throttle plates that is exposed to vacum when the throttle is opened. I've seen the throttle plates so warped on some carbs that the vac port is exposed to idle vacum. That's why you pull the hose off of the dist advance (or carb side) when statically timing your engine.