123 Distributor vacuum advance set up and curve, Advise on seting up the vacuum advance curve on 123 distributor Options

[Clydeskeeper]

I have searched the forum and watched too many YouTube videos. I am either missing the answer or just don't quite understand.
I am replacing my distributor with a Bluetooth 123. I am a little confused on setting up the vacuum advance curve and maybe even the mechanical curve. On a basic level, I understand that it needs to go from a static of 10 degree at idle up to 27 or even a little more at 3,500 rpm's. Of the videos I have watched, seems like most are not even using the vacuum advance part and just using the mechanical to achieve the above curve. Others go into details I just don't understand including using the vacuum to retard the timing at certain rpm's.
Is there a simple answer and old guy like me can understand? I grew up with cars that actually had mechanical distributors with points and carburetors for fuel delivery. So these concepts are not completely foreign to me.

Just for reference, the engine in question is a modified 2 liter that is now 2549cc with dual 48 Webers.

I await your thoughts, should be interesting at always.

Robert!

[emerygt350]

I use setting 1, seems to do well for my engine. I have ported vacuum and use the vacuum advance.

The problem with the retard is the original design was supposed to fight the advance, then in late 74 or something they dumped the advance and that was lost. Then to compound that the 123 retard is on or off and sensitive to the slightest vacuum (I think I measured it turning on the retard with as little as 3 inhg. Probably less. Your retard port on the Tb can see that at cruise and even when you start cracking the throttle. I found my car was retarding the timing at all the wrong moments. The original wouldn't have reacted or at least reacted much to such a small signal.

It will reduce your idle of course but my car is at 8 degrees at idle with my leaky idle screw all the way in and idles at 900. I could go lower if I didn't have a leaking idle screw.