vacuum advance

The car will run just fine with a bad one, but if you mess with this at the parts store, you are looking for trouble.. Personally, I'd yank out the dist. It's a good time to look over the rest of the dist. for wear and other potential problems.

As I said, find a port on the engine that has manifold vacuum. Temporarily hook the advance to that port and see if the timing advances. Usually you can tell just from the increase in idle speed.

That is......

Expose a manifold vacuum port. Hold your finger over the port and listen to the idle. Hook the vacuum advance can hose to the manifold port and the engine should noticeably speed up.

If no change in idle, the vacuum can is bad.