Concur w/Ed, 1st thought is a vacuum leak,possible at the dist vacuum adv unit, the line to it or at the manifold.
Plug the vacuum line fitting at the manifold and test.
Another test to try is while it's idling, remove the air cleaner and cup your hand over the carb in an attempt to cover it up. This will enrich the fuel/air mixture. If idle picks up you've got a vacuum leak, if it trys to stall out you may not.
Like Ed said with the vacuum line connected the whole dist should rotate when you increase rpm, make sure.
Good luck
Dave
