Jetcopterpilot,

I will admit the 1960's system was somewhat crude, compared to newer computer aided technology; however it won't give the problems that you say it will connected to manifold vacuum.

Vacuum advance responds to engine load and rapidly-changing operating conditions, providing the correct degree of spark advance at any point in time based on engine load, to deal with both lean and rich mixture conditions as in accelerating or decelerating.

When you disconnect the vacuum hose to the dizzy during tuning, that is to allow you to set the static advance only. The advance will be further increased when the vacuum line is reconnected, probably 10-15 degrees, so if your static advance is 12 degrees, the total timing is 25 or so degrees at idle when the vacuum line is reconnected. The timing is never retarded.

The technology seems simple, but there are many confusing articles out there that have muddied these discussions.

So far, we have not even talked about centrifugal advance which is also part of this equation and interconnected as well.

I am sure I will be hearing more about this, and I will respect your opinions, I just may not agree with them