Hi Hans,

Assuming this is really the vacuum advance unit I think it is, that's what I like about it -- it's vacuum advance.

Without getting into a long discussion of the theory, what I do is set the timing for best performance with the vacuum disconnected, and then connect it to the full manifold vacuum. This has no affect on full-throttle, but improves economy at part-throttle.

It's perfectly fine for the timing to read 28-30 BTDC at idle, although that takes some getting used to mentally.