The vacuum advance will go away almost as soon as the manifold vacuum drops as a load comes onto the engine. Its only real function is to squeeze a little more fuel economy out of the engine when it's running at light throttle cruise. You can see this by jacking up the rear wheels and getting them spinning at highway cruise speed, then ride the brake a little while watching the timing mark. As the vacuum starts to drop as the load comes on, the timing will drop back to your "power" setting. I used to do that demonstration for my students pretty often.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!