 123 Distributor vacuum advance set up and curve, Advise on seting up the vacuum advance curve on 123 distributor |
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| Clydeskeeper |
 Jul 15 2025, 01:10 PM
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Newbie  Group: Members Posts: 3 Joined: 21-June 25 From: El Cerrito Ca Member No.: 28,851 Region Association: Northern California  |
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! |
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| emerygt350 |
Jul 15 2025, 03:48 PM
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Advanced Member Group: Members Posts: 3,046 Joined: 20-July 21 From: Upstate, NY Member No.: 25,740 Region Association: North East States |
Don't worry about the vacuum advance. Just set the curve to what the engine likes. 10 at idle seems a bit high to me but others with Bluetooth 123s will chime in.
If you like, you can then set a vacuum advance, but you need ported vacuum to do that. If you want you could set it to a 7 degree advance when the 123 sees vacuum on the port. If you have hooked the line to ported vacuum on your webers it will then advance the timing at cruise and improve your mileage and maybe reduce temps. If you are just racing and having fun with it, it may not be worth your time to do anything with the vacuum advance. Retard was an old thing to reduce emissions at idle. Don't mess with that, it's a mistake in the 123. The original design had an analog response to vacuum but the digital does not and it can end up retarding your timing at cruise. A bad idea |
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Posts in this topic
Clydeskeeper 123 Distributor vacuum advance set up and curve Jul 15 2025, 01:10 PM
wonkipop
I have searched the forum and watched too many Yo... Jul 15 2025, 04:07 PM rjames
Tell me more about this. I've got a non-blue... Jul 16 2025, 12:12 AM emerygt350 I use setting 1, seems to do well for my engine. ... Jul 16 2025, 05:03 AM
rjames
I use setting 1, seems to do well for my engine. ... Jul 16 2025, 09:27 AM wonkipop
I use setting 1, seems to do well for my engine.... Jul 17 2025, 08:31 PM Clydeskeeper Thank you all for you knowledge! I think I now... Jul 16 2025, 12:44 PM emerygt350
Thank you all for you knowledge! I think I no... Jul 16 2025, 01:29 PM Clydeskeeper Mr emery.GT350,
You bring up a good point and a d... Jul 16 2025, 06:46 PM |
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