Hi, is there a remote vacuum advance module that you can run a vacuum line to and plug it into an MSD to get vacuum advance on a locked out distributor? I think I remember seeing some kind of MSD years ago that had a vacuum port, but I can't find it on the web. I know that sounds like a weird thing to want, but I find that my drag & drive Hemi runs way better and gets better fuel economy on the street with vacuum advance. But there is a firewall clearance issue with having a vacuum can on the distributor. (Early Hemi)

Thanks, Joel

The MSD boxes with the vac reference you are thinking of was probably the 6 BTM IIRC. They were for retarding timing with boost, I am not sure if that would work the other way or not. I am pretty sure they no longer make that model.

You may be able to achieve what you want with a 6AL2 programmable but you will need to run a map sensor, i’m not sure if it will let you adjust timing under vacuum though. It may be boost only.

GTX Matt is correct. I run a 6AL programable and it has a connection for a GM MAP sensor. You go to your fuel/timing map and add timing per manifold vacuum. Haven't used it, but its there. The 6AL Programable is a very nice piece.

Great, thank you!

You can program a vac advance curve on the 6AL programable down to 29 in/hg (1 Bar or -14.7 psi) using the correct MAP sensor (MSD lists it as PN2311, 1-bar for N/A engines). If you have an MSD Grid, there is also a module available (PN7762) which allows you to do the same but can also map ignition timing for boost up to 45psi (3 bar).

Page 13 below references the vacuum / boost control on the 6AL (programable).

https://documents.holley.com/265ea1b84039cc125d4c605e79a20985a08a9c12.pdf