Shelby Tach wiring?

Another question this time on the tach. The previous owner added the MSD 6AL system, this system removed one of the dual points and added an amplifier to the distributor. After the installation the Shelby tach no longer functioned but the previous owner seemed to accept that. I contacted MSD and they said I need the 8920 Tach Adapter which I bought. The instruction are pretty simple, plug the white wire into the tach output on the MSD box, black wire to ground and the red wire to the original trigger wire (original coil + wire).

I located the wires out of the Shelby tach, one is blue, one is red and one is black. I figured the black would be ground. The question concerns the red one and the blue one. One should be the 12V supply (for the light and power) the other should be the original wire to the coil (I suppose).

Does anyone know which is which?

Has anyone else added the MSD 6AL system to their car? It seems to work very well as the car will fire off in just a few revolutions even after setting for a week.

 

Z. Ray,

Thanks for the information, I do have the instructions but could not figure out which wire to tap the red wire (from the tach adapter) to. I never would have thought or known that the black wire is not a ground, I appreciate the tip. I will hook up the red wire to the black wire tonight and let you know how it works.

Ron

 

Thanks for the link, I did find an "original type 1966 Shelby Tachometer wiring diagram" on Tony Branda, it shows 4 wires out of the tach, a green one that goes to the (-) side of coil, a red one that goes to the ignition switch and then on to the (+) side of the coil, a "short" red that is for the light and the black that goes to ground. I will have to look closer at the wires I found last night and with the help of the wiring diagrams from your link hopefully figure this out.

Ron

 

Z. Ray,

It is hooked up and works perfectly. When I got home tonight I traced the end of the black wire and it plugged into a red wire. Using the splicer from MSD I tapped into it, plugged the red wire in, then hooked up the white wire to the MSD box and the black to ground. Pretty easy.

Now I just need to find a place to mount the tach adapter, I currently have inside the car and ran the white and black wire through the firewall. If I cannot find a suitable place in the car I will put in the engine bay near the MSD box.

Thanks for all the help.

Ron