to begin with, set the timing the way you are supposed to, using the ball and pointer. Completely disregard the octane selector, it really has no use. At least there is none that I have found, I have never touched it in 30 years. Once you set the timing with the ball and pointer, you can tweak on it with the vacuum gauge, although after the above mentioned 30 years I gave 'er a go with the vacuum gauge. It increased the vacuum slightly,(maybe 3 inches) but as far as I could tell there was absolutely no difference in performance. (if you can call that performance) It was however more difficult to start. Before I messed with it, all I basically had to do was stomp the starter pedal to the floor, let it up, and it was running. So I put it back using the factory recommended method.
