[Gaz64]

With a centrifugal advance distributor, the rotor tip will be aligned to the cap terminal at any rpm.

With a locked distributor, and electronic advance, (which is really a retard), the rotor tip only aligns at about the midway point in the advance curve.

So if we want 30 at 3000, and 14 at idle, a curve of 16 degrees gets split to give 8 each side of middle. So at at 22 degrees, the rotor will be in the middle of the terminal.

You can see this with a timing light, as you rev the engine the spark should go from one side to the other. Otherwise you risk crossfire within the cap.

An adjustable rotor or adjustable pickup is necessary for this to be possible.

Gary