Tachometer compatability

[Dunerider777]

I have just got 6s1164 back running again. All the gauges are working except the tach. When we rebuilt the motor we decider to put a pertronix module in the distributor instead of the dual points. I have seen where some say that the tach will not work with pertronix and that it will. Looking for a definitive answer. Thank you.

[1967 eight barrel]

Yes, they will work with the tach.  Which Pertronix are you running?  I had the same issue with my 1967 Shelby and the factory tach with a Pertronix II.  If you want me to walk you through it, PM me.
                                                                                           -Keith

[Rocket]

6S550 has had a Pertronix on it for a couple of years with no problems. If I did any rewiring, it had to be at the distributor. Ron

[jk66gt350]

No issues if it's wired properly.  I've had a pertronix in 6S1575 for about 15 years.

[1967 eight barrel]

You forget there are three different Pertronix units. The II and the III will not work with a tach without running an additional lead. As a matter of fact the Pertronix I usually causes incorrect readings or a non-functional tach on current sensing tachs that Ford used. The instuctions that come with the Pertronix are not compatible with factory tach vehicles period.
                                                                                    -Keith

[jk66gt350]

Your comments reminded me that the instructions I used to install mine, were instructions I got from the guy the rebuilt my tach when I told him I was going to switch to the pertronix unit - not the pertronix instructions.   It's been a while.

[rraceme]

Hey I have a question about tachometer wiring. On original 1966 GT-350 cars, how was the tach wired? using wires under dash like a rally pack? or driven off negative side of coil?
thanks, Fred

[DennyD]

Attached are wiring diagrams for both the Pertronix set up, and the original Tachometer. Thanks go out to Kieth Champine for these photos. 

[1967 eight barrel]

Ford tachs are current sensing. You also do't get 12V to the coil  EXCEPT when you are engauging the starter. After that it drops to about 6-7V.  If you actually read directions, the Intructions tell you that you must have 12v constant.  You can avoid digging through your wiring and unplugging the resistor wire, which is VERY difficult to do on 67 and later vehicles. Simply pull a wire a 14 gauge wire though the grommet to the positive wire on the Pertronix. The wire can either be ran to the ignition switch 12V ign constant hot, or the red wire that goes to the tach. The black wire from the Pertronix goes to the negative side of the coil. Use the nut. Slid the black Ford wire that comes from the harness onto the negative post of the coil.  The failures that many blame Pertronix for will be an issue of the past.
The II and III version are absolutely dependent on 12V constant.  Many get away with running the Pertonix I for years sometimes.
I have the Pertonix II on my Shelby. It's been there 14 years, never an issue. I like the two because it automatically adjust the dwell.

                                                                                                                 -Keith