'51 8BA - What is the correct ignition setting?

[waynet]

Gentlemen,

When I first checked the ignition timing both the pointer and the pulley notch lined up with the engine running at an idle. When I rechecked the timing with the vacuum line disconnected, and left open at the distributor, the pulley notch was way passed the pointer by at least 25-30deg after top dead centre.

What is the correct procedure for setting the ignition timing?

Thanks as always.