1968 Plymouth Valiant First Gen HEMI
I tried not to completely waste the winter so I spent some time figuring out some things that I would normally do much later in the project. As I mentioned the car is being built to be a dependable long distance cruiser. That being said parts do fail.
I’m going to be running an MSD 6A box on the car. I like them for some builds and was using a MSD 6AL box on my 57 Plymouth. I had had an MSD box on another car fail just prior to doing the wiring harness on the 57 so was looking at picking up a spare MSD unit to carry with me. For me the MSD box was a little pricey to have one sitting in the trunk “just in case”. Then I would still have to remove the old MSD box mount the new one and wire it in. Not a fun prospect when you’re sitting on the side of the road in the middle of nowhere at 3AM.
Anyway I sat down and figured out the wiring I would have to do to mount and use a standard MOPAR ECU as a back-up system. I wanted it so if the MSD failed, I could simply just unplug the MSD and plug in the MOPAR ECU start the car and be on the road again. I decided I wanted to use the same system on the 68. I’d kept a copy of the wiring diagram but the wiring had changed slightly on the MSD I had from the last system I’d built (15 years ago). I started from scratch on the wiring diagram.
These are the factory wiring diagrams for the MSD 6A and Chrysler ECU I started with.
And these are the wiring diagrams where I connect the units to 8 pin plugs.
And this is the diagram showing how the wiring harness is wired to the plug either the MSD or ECU into the cars system.
A word of caution to anyone who may want to build one of these back-up systems. These diagrams are designed for a specific MSD box going into a specific car. MSD wiring can change slightly from model to model (and the year it was built). It will be up to you to verify every circuit on your particular vehicle.
I also started looking at the dash/gauge cluster in the Green car. It might have been OK when the car was mostly on the strip, but left a bit to be desired for something that gets driven on the street on a regular basis. The factory cluster behind the tach actually looks pretty presentable, it even looks like they installed new gauges in it…..unfortunately nothing appears to be hooked up.
Oh well that’s what I built a parts car for. I didn’t mind using this for a basis to an aftermarket gauge cluster. And I could pretty much just work at the bench when my back bothered me.
I already had the speedometer, tach and 1 ½” gauge trio. I could not find a 1 ½” fuel gauge however and finally settled on a 2” gauge. Although not exactly the placement I would have liked had I found a 1 ½” fuel gauge this is what I came up with.
I’m using the original locations for the headlights, wipers and hazard flashers (plus added a new switch for the fuel pumps) so I needed a portion of the original back plate.
I’ve still got a little to do/re-do on it but overall I’m pretty happy with it.