First post here. I picked up an unused Davies Unified Ignition racing coil distributor with mechanical advance for 60 bucks on Facebook marketplace. Cool find but I wanted to use it in my computer controlled TPI setup. So I locked out the mechanical advance with a locking plate and modified the pick up coil connection to go into my 7 pin Dyna Mod ICM. Ran my 4 pin harness through the rubber plug where an optional vacuum advance would go (since this is the non vacuum advance model) and plugged into the other 4 pins of the ICM.

​​​​​​It works! It stays on my base timing of 6 degrees when EST is unplugged and changes timing as need by the ECM when plugged in.

​I wanted to experiment a bit so I removed the lockout plate and to my surprise it runs and idles really good but I'm too scared of taking it for a drive like that. I think the ECM adjusting the fuel and air would get confused and cause issues.

My question is what would happen if I did run it like that?

 

Nothing would happen, with the "Fuel and air"; it'd run (that part), same as it does now.

What WOULD change is that you'd be over advancing the ignition timing part, so you'd have whatever advance the ECM is putting in, plus whatever advance the Mechanical is putting in. I'd run one...or the other, but not both.