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!

[Clydeskeeper]

Thank you all for you knowledge! I think I now know more! (IMG:style_emoticons/default/smile.gif)

I think I will just set it up with the mechanical advance curve and disable the vacuum advance curve. Seems to me, because of the advanced modern features, I can get all the engine needs with the mechanical only.

Question for the engine masters? I am inclined to mimic the stock advance curve, 7 - 10 degrees at idle up to 27-30 or even 35 degrees at 3,500 rpm's.

Given that my engine is so much larger than stock, 2549cc, any considerations for the increased displacement?

Thanks for your input, I am going to tackle this install this weekend and see if I can get more of the bugs out of my 914.

[emerygt350]

Thank you all for you knowledge! I think I now know more! (IMG:style_emoticons/default/smile.gif)

I think I will just set it up with the mechanical advance curve and disable the vacuum advance curve. Seems to me, because of the advanced modern features, I can get all the engine needs with the mechanical only.

Question for the engine masters? I am inclined to mimic the stock advance curve, 7 - 10 degrees at idle up to 27-30 or even 35 degrees at 3,500 rpm's.

Given that my engine is so much larger than stock, 2549cc, any considerations for the increased displacement?

Thanks for your input, I am going to tackle this install this weekend and see if I can get more of the bugs out of my 914.

If you can get yourself on a chassis dyno, I would figure it out there. Depending on your quench and compression and all that change in volume, I wouldn't assume 7-27 is right or good for your motor. I tuned mine originally on a dyno and then over time by my butt and the feel and the head temps and the MPG. I have found a sweet spot at 8-28ish. Any more advanced and the idle is high and the temps (both oil and CHT) go up. Any lower and the engine is lame and the temps also go up. They will also be able to tell if your mixture is looking good at cruise and WOT. Even if you don't pick up more HP I guarantee you will get more area under the curve by going to a dyno. I went from a peak at 4k to a flat line from 3k to almost 6k by playing with the mixture and the timing at the dyno. Dyno for the shape of that curve for sure.