Hello all,
I am having an issue with my 67. The issue being that once I changed out the wiring system to a painless one, I am burning out the tach. I have a Hyfire box and Unilite distributor running to a oem style in dash tach and it is frying the diodes on the back. Is there a way to make this system work with an old style tach? I have replace the diodes twice and it works for a little while before burning out. I have contacted Mallory and they did not have any answers. He told me I could try a 29078 tach adapter but it would most likely not solve the problem. I think there is too much voltage coming into it. Any help would be appreciated!

 

From what source are you hooking the tach up? I have an MSD 6AL box, and my (aftermarket) tach hooks up to the tach output on the box. It does not hook up to the coil like on a conventional ignition system. I haven't used it, so I don't know if your Mallory box works the same way.

 

The instructions show the tach hooks up to the yellow wire from the box. Is this how you hooked it up? You don't want it going to the coil.