Do I disconnect the vacuum hose to the distributor when setting dwell like when setting timing? Or do I leave it connected?

The only reason to disconnect the vacuum lines is to remove the vacuum from the system. It will raise the idle, nothing more, when removed for setting the dwell. IOW, no. The Cap'n

dwell is not effected by the vacuum lines, the timing is, but not the dwell. dwell is set up by the pionts gap only.


one thing I highly recommend you do is convert to a Pertronix ignition, around $100 will get you dead nuts on timing every time (no more drift), no more worn parts to replace, and dwell is no longer an issue at all. you will be running at the timing you set it at each time. Very relaible system. and saves labour it is a set once and forget system (actually I have checked my timeing since putting on the pertronix, it has never ever drifted in a couple decades of use on several cars.)