Pertronix install vs. wiring diagram

Phase has nothing to do with timing, even though phasing does change timing to some degree, and while mechanical advance affects timing but not phase, VACUUM advance or points gap (or position of sensor) affects both timing and phasing.

Rotor phase put simply is "that point in the distributor rotation at which the spark is triggered" compared to "that point in rotation where the rotor is instantaneously"

When the vacuum can moves the plate in the distributor, this changes the points position, and changed the timing. THIS ALSO changes rotor phasing. But it is "in the design." That is, between the width of the rotor and the cap contacts and the "target" phasing the maker built into the thing, even though the thing moves, the contacts "should" still be inline. On one extreme, or the other, of vacuum advance, the rotor might be "corner to corner" with the approaching corner of the cap contact. On the other extreme, the rotor might be "corner to corner" with t he LEAVING side of the contact.

But "if something" is wrong, IE bent vacuum advance, distributor wear, who knows? The spark might be occurring when the rotor is BETWEEN cap contacts thus causing the spark to jump, and causing misfire to the adjacent cylinder.

Review those links I posted. There's one or two MSD videos on the subject, they are referring to an adjustable rotor which of course we don't have.

The last thing that also changes both phasing and timing in "normal" terms is points gap, or dwell. If you gap points "too wide" this advances timing, and as they wear, naturally towards "closed" the timing retards. If you were to adjust them to extremes, IE barely closing, they are so wide, or barely opening they are so close, you would find that rotor phase also changed "some."

The thing in the end that is bothering me, here is that you say timing changed some 20 degrees. That is a BIG change and I'd want to find out why.

Let me set up a DRAMATIC scenario in your mind. Let's say we have a working distributor. All set up and timed. We "stop" this at some point and do not move it, and we stop it at the instant the spark triggers. The ROTOR will be pointing "somewhere." We do not move it.

Now, we magically move the points someplace "else." We move them 10, 20, 30, 35 degrees away from this point we stopped. Now we position the distributor so that the points are again triggering. WHERE is the rotor pointing? It is no longer pointing to the plug tower it was originally, it is, rather, somewhere in between.