If the dist vacuum advance does not advance at idle you don't need to disconnect it. These are hooked to ported vacuum & will not advance till the throttle is opened a little. If a dist. Is hooked to full manifold vacuum it will advance at idle & would give an incorrect reading of the initial advance. After you set the timing you can taylor it a bit with the octane selector. You can run more advance then called for because today's gas has more octane then they had back then.
