Classic/Antique Car Repair: Ignition coil to distributor question., petronix ignition, mgclub

Question
Have converted my 51 Daimler, 2 1/2 liter engine, to negative ground.  

My distributor has been converted to a Petronix electronic system.  There are two wires coming from the distributor one is RED the other is Black.

I've misplaced the schematic for the Petronix and don't know where the wire should be connected.

My question is, which wire goes to the coil (red or black)?  Where should the other wire be connected, or is it not used?  

Thank You
Larry Reynolds

Answer
Hi Larry,

Your "Petronix" ignition system is an aftermarket ignition system. It is often used as a replacement to the Lucas system on MGs and I have seen the system on MGs. Your concerns about connecting it up wrong are not unfounded. Many of those aftermarket ignition systems can be destroyed if connected up wrong. My memory is not reliable on this although I remember that both went to the coil. Red to power and black to negative on a negative ground system. I don't want you to completely depend on my memory on this so I would suggest you put it on the MG message board. There are a few messages on the board about Petrolix but I didn't see any addressing the wiring hook up. Go to this site (http://www.mgclub.org/bbs/index.sht)and click on "Post a Message". If you get several others saying red to pos. and black to neg. on the coil you should be safe.

If that don't get you an answer e-mail me and I will dig further.

Howard