Hi,
This issue is further complicated because of the change from an externally resisted coil to an internal resisted unit. The inline "pink" is there to reduce the "run" voltage to 6-8Vs, not so much, to reduce the operating volts to the tach, but, to benefit the coil (factory, that is). These early tachs (until the early 70s) sense current (amp) not voltage.
Otherwise, running a separate 12V feed to the red side of the Pertronix is easy-peasy.
I'm thinking the tach will not be damaged so much as the reduced voltage to the coil, both from the "pink" and the internal resistance.
We need to hear from a learned automotive electrical expert.
Just trying rationalize the operation.

 

OK guys this what the Pertronix tech told me to do. They were real good about getting back to me about it too. I believe this answers all my questions and hopefully all yours also.

 

Yep, I had a feeling. So you must use the factory coil to keep the tach working right? Does Pertronix have a replacement coil that will work?

 

The car already had a Ignitor ignition module when I bought it and I wanted to add a better coil. I explained to the Pertronix Tech that I am going to use a Pertronix 40,000 volt Flamethrower coil. Thats where I got directions with the coil to use a standard wire to get 12 volt to coil instead of the the resistor wire. He sent me the wiring schematic on how to use both. I haven't wired it yet though, This next week I should get time to do it.

 

Hi,
Their schematic, is pretty much, what I described. By-pass the pink with the 12V to the Pertronix's red. However, where the issue lies, is the tach's connection to the coil through the OEM pink and it's pre-determined resistance value designed to work with the factory coil. If you sub a different coil, with a different resistance value, how does this affect the tach?
Now, this being stated, the inline pink wire between the tach and the coil, is there for the benefit of the coil, not the tach. Correct? If this is the case, Whose ever go fast coil you use, and it has the "built-in" capability to reduce the voltage during the run cycle, then you will be fine. Then you should be able to remove the pink connection.
We're dealing with current sensing (tach) not voltage, wherein, the tach get's it's signaling pulses.
I would quiz the Pertronix's folks on this. But they need to know the tach technology as it changed in the early 70s. Some of those guys may not have even been born? LOL.

 

I did inform the Pertronix tech that I was using an oem Rally Pac
type tach and that his answer to me was with this in consideration. I did wire the coil up today and took it for a test drive and it ran great. Starts alot easier, I mean immediately.
However now I have another problem. I pulled the dash out to hook up the bypass wire and the speedo cable came unhooked. it must have been held on by just a couple of threads and I had a terrible time trying to get the drive cable back into the speedometer. I thought I had it Ok and threaded the nut back on. When I was test driving it the speedometer quit working, so, out comes the dash again.

 

Hi
Yeah my friend, I have been there! You need a kid with little hands. LOL! But, you can do it. It just takes patience. I know, I really know.
Happy Motoring!