I asked this over on FABO but I didn't exactly get the info I was looking for so I figured I'd try here. I'll try to simplify it a little.

I am putting an MSD 6 AL into my small block '71 Duster. Since the MSD does not require the ballast resistor, I would like to eliminate the ballast resistor and all associated wiring from the harness.

As I've read here and elsewhere, the smaller red signal wire from the MSD must be tied in to the ignition 1 and 2 circuits (start/run, blue + brown wires).

Instead of splicing the ign 1 + 2 wires to the red MSD wire, I want to use a 5 pin ISO relay to connect the start/run circuits to the MSD signal wire.

Here's what I'm thinking:

Take the blue and brown wires out of the back of the B.H. connector on the dash side. Crimp on suitable female connectors to connect to the relay terminals.

So using 5 pin relay;

Brown wire to 87 (crank)
Blue wire to 87A (run)
Red MSD signal wire to 86 (powered by 87 then 87A for each switch state)
Battery + to 30
Ground wire to 85

So as I understand it, the ignition switch would energizes the brown wire pulling the coil in and powering the red wire at start. Then when the key is released to run, the blue wire is energized and the red wire should still remain energized. I may have that sequence crossed up but you get the idea.

Only thought I had was there is a moment when the circuits switch where there is no power. I would think it wouldn't be an issue with a non-computerized system. I read here that a capacitor might work but would that really be necessary?

This would be behind the dash so these wires would no longer be going through the bulkhead and I could eliminate the B.R. wires from the harness.

Sound OK?

- Greg

Why complicate it.Just solder a 12 or 10 gauge wire at the ballast.It eliminates it but looks stock.Ive had my MSD thru the ballast for 15 years.No problems.Rocky

I just use a jumper wire and leave the BR there in case I ever want or need to switch setups.

Way too complicated. Just jumper the IGN1 (blue) and IGN2 (brown) together at the switch and run a single wire from IGN1 to the MSD red wire. I do this by soldering a piece of brass rod between the two terminals.