Hi Johnny,

You have the right idea. The advance unit should 'hold' for a period of time or it is leaking and should be replaced.

On the rebuilt units, I don't think you would want one of those except for a driver. All the ones I have seen that are rebuilt are so crude you would be ashamed to raise your hood. I don't have a clue as to the material they use for the diaphragm when they rebuild them.

The Filling Station now offers a rebuilding service for vacuum advances. I have had some very rare (and big dollar) advances done from this service that the Filling Station provides, and the quality is top notch! It is so good in fact, that you can't hardly even tell that the vacuum advance has ever been apart. And, I have never had one of these fail yet! I highly recommend their rebuilding service!

Vacuum Advance Update!: I have just learned that the Filling Station also now has in stock a supply of reproduction vacuum advances for 1939-51 Chevrolets, and they also have a very limited supply of NORS vacuum advances for the 1952-54 passenger cars, so get them while they are still available!

In the later 40's early 50s there were a lot of shops that did not have sophisticated equipment but early in the 50s and beyond there were machines such as the one I trained on "Sun" which had a vacumn pump, and a distributor drive with tach to check the vacumn and mechanical advance.