Thanks for correcting us, Roy,
The vacuum to the vacuum advance is indeed different from the vacuum produced at the carburetor/intake-manifold.
There have been a few vacuum advance posts lately. Before replacing a non-moving vacuum advance unit, I disconnect the line at the vacuum advance unit and attach the line to a rubber hose connected to a vacuum gauge. Then, rev the engine and check the vacuum readings as the revs go up and down. If the readings fluctuate but the vacuum advance had not been moving, . . .
