Rotor changes timing, 123 running fine, but? Options

[mgphoto]

So my engine has been really running fine except for a miss that seemed to come on at about 3200 rpms. I'm running the 123 D Jet version #B switch and no vacuum connection to the dizzy. I've pulled the timing back to 26* and I'm using regular gas with an MMT additive to control ping. This setup has been working very well as I've been testing different brands of the additive for effectiveness.
The miss I've attributed to cap, rotor and wires. I replaced the cap and rotor and before replacing the wires I took it for a spin.
The miss seemed to be gone but the ping I had tuned out was back?
I hadn't moved the dizzy, I tightened the clips holding the cap but no other change.
So I pulled the cap and took out the rotor to see what might have changed.
The new cap was identical to the one that came with the dizzy, but the rotor not so much.



I suppose that could be a 2* difference in the rotor pickups?
I put in a rev limiting 5850 rotor I had in my stash and now no miss and no ping!
If there's an issue it will find me...

[MarkV]

The rotor doesn't determine the timing. The reason that the end of the rotor is relatively wide (it looks to be about 20 degrees of arc) is because its only job is to get the spark from the center terminal on the cap to one of the outer terminals.

Something else is going on.

--DD

I guess I disagree....when you hook up a timing light the light flashes at the rotor passes the #1 terminal on the distributor cap. If you have a rotor with a wider tip it's going to change when the light flashes and change the timing. (IMG:style_emoticons/default/confused24.gif)

[Olympic 914]

The rotor doesn't determine the timing. The reason that the end of the rotor is relatively wide (it looks to be about 20 degrees of arc) is because its only job is to get the spark from the center terminal on the cap to one of the outer terminals.

Something else is going on.

--DD

I guess I disagree....when you hook up a timing light the light flashes at the rotor passes the #1 terminal on the distributor cap. If you have a rotor with a wider tip it's going to change when the light flashes and change the timing. (IMG:style_emoticons/default/confused24.gif)

WRONG... The light flashes when the points open, that's when the coil fires. the width of the contact on the rotor would only increase the possible range of advance or retard. the spark isn't triggered when the rotor passes the contact in the distributor. it fires when the points open, the position of the rotor only determines which plug fires because the current goes to the nearest one at the time.
Dave is correct.