What are the +/- of a Pertronix Ignitor II vs I?

7173Mustangs.com

Help Support 7173Mustangs.com:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Thanks for the replies everyone. I'm going to go with the PII as this car doe snot have a factory tach.

Kevin.
I went with the PII, along with the recommended coil and wires. No issues. Full disclosure car has been in paint shop Prison since May.

Went in with no issues and great results. 351 4V m code
 
Rhig1959 - I’m confused - so you connected a pos 12v wire, OTHER than the 12v coming from the ignition switch, to the coil’s pos post?

Where is the other wire from the tach connected?

In this diagram from Fords 1971 shop manual, the tach is wired between ignition-switched power and the coil’s pos post.

IMG_2959.jpeg
Is this proper? And even with a Pertronix III?
 
The PIII requires a full 12V and is basically incompatible with the factory tach setup without an adapter. With all of the original PO's aftermarket wiring, it will be near impossible to decipher exactly what was wired to what...I'm not surprised the factory tach wouldn't work.
There's been some discussion of the PIII being a piece of junk as well.
Once one goes to an aftermarket multispark ignition system, changing the tach over to what Rocketman offers is the smartest solution.
 
The P3 is a multi-spark ignition, so your factory tach will most likely not work, or will not be accurate if you can get it to. If you want to keep the P3, the solution here is to send it to Rocketman's Classic Cougar Innovations and have it converted to a "modern" three wire tach setup. Be sure to let him know you're running a P3, as some tachs require a resistor inline to filter out the multiple sparks.

If you change to a P2 or P1, the factory tach will work properly as long as it's wired correctly, in series between the coil (+) and the ignition switch. The Pertronix module needs to be powered separately off another 12V feed, which can be a relay or an ignition switched source. The aftermarket harness complicates things, so if you have any documentation, knowing the manufacturer and model of the harness would be a huge help.
 
I have a pertronix 3 coil and the kit that goes inside a stock distributor.
I also have a rocketman tach conversion and a carb cheater system. Both of those are able to read the correct RPMs off the pertronix 3 coil without having to do anything extra.
 
I know it was back in 2012 after my engine was rebuilt (for the first time) and the builder chose to put in a PIII, I'm sure he just happened to have it on the shelf, but unless Pertronix have done a total redesign of the plastic "bearing" between the plates, you're likely headed for trouble in a few months. In my case, that "bearing" wore out to the point that the upper plate was seen moving both laterally and vertically on a distributor machine. It was sent back to Pertronix and they replaced it with a PII and coil, no questions asked.
Electronically, the PIII might be excellent especially with a non tach, or conversion tach car. I really liked it for that aspect and with the adjustable rev limiter feature.
My point here is that unless there has been an improvement with the Ford version, be aware that your timing may start to "wander" down the road.
It would be a real shame if Pertronix have not corrected this problem. They needed a design similar to the DuraSpark distributor or even the Boss dual point that has an actual bearing between the plates, but the "bean counters" rule!!
 
I had a long discussion with the owner along with some more pictures. The problem is even worse than what was already described. The underdash harness (and probably the headlight harness as well) was all aftermarket wiring with a bladed fuse box. Most Ford connectors were re-used and spliced into the aftermarket wiring. What I think happened is that the person who did the wiring (about 15 years ago) thought the tach was a 3 wire affair, and the wiring was put in place along with the PIII ignition system. The problem is that the current tach is the factory 2 wire current sensing device and there's no input wire for the tach on the underdash side. Without documentation on what colored wires do what (a major problem with aftermarket solutions, particularly after the car has passed hands), there is too much work to be done to reverse engineer the system. With no available used 71 tach underdash harness available, the owner is basically SOL. He's not real comfortable starting from scratch with another aftermarket system either. Although the car runs, the tach does not. I advised him to flip this car and cut his losses. Fortunately, the car was gifted to him.
 
It is with both relief and sadness that I cannot resurrect what at one time was a fine example of '71 Mach 1.

My first car in high school was a blue '71 4 speed, Mach 1 with a 351C 4V, manual steering and no AC. I loved the shit outta that car (and who wouldn't if it's their first?), even in the sweltering summers of Sonoma, California. I gave that car to my younger brother in 1978 when I left Cali to live with my high school sweetheart going to college in Boston.

Just months ago my brother "gifted" me this car. He had it since 2010. Another 71 4spd Mach. His gesture nearly brought me to tears. What goes around came around, I figure. He wasn't very mechanically inclined, and so farmed a lot of the work out over the years. I accepted his gift with grand plans to resurrect it to it's former glory. However, the deeper I dug into it the more I realized that, with the help from Midlife, Rocketman and my body-guy, I'm really using a tub of sentimental emotions to polish a turd (my term, not theirs).

So, I'm going to button it back together with crazy wiring, a non-working tach, needed bodywork/paint/interior panels, etc, and throw a polish on it to drive it a little more before flipping it.

Thanks to everyone who gave me their .02. And moreover to those who were more interested in providing sound advice instead of letting me continue throwing money at it. Class acts you are.

The right one will come along.
 

Attachments

  • IMG_1754.jpeg
    IMG_1754.jpeg
    370 KB · Views: 1
Last edited:
It is with both relief and sadness that I cannot resurrect what at one time was a fine example of '71 Mach 1.

My first car in high school was a blue '71 4 speed, Mach 1 with a 351C 4V, manual steering and no AC. I loved the shit outta that car (and who wouldn't if it's their first?), even in the sweltering summers of Sonoma, California. I gave that car to my younger brother in 1978 when I left Cali to live with my high school sweetheart going to college in Boston.

Just months ago my brother "gifted" me this car. He had it since 2010. Another 71 4spd Mach. His gesture nearly brought me to tears. What goes around came around, I figure. He wasn't very mechanically inclined, and so farmed a lot of the work out over the years. I accepted his gift with grand plans to resurrect it to it's former glory. However, the deeper I dug into it the more I realized that, with the help from Midlife, Rocketman and my body-guy, I'm really using a tub of sentimental emotions to polish a turd (my term, not theirs).

So, I'm going to button it back together with crazy wiring, a non-working tach, needed bodywork/paint/interior panels, etc, and throw a polish on it to drive it a little more before flipping it.

Thanks to everyone who gave me their .02. And moreover to those who were more interested in providing sound advice instead of letting me continue throwing money at it. Class acts you are.

The right one will come along.
Be honest with whomever buys it.
 
Rhig1959 - I’m confused - so you connected a pos 12v wire, OTHER than the 12v coming from the ignition switch, to the coil’s pos post?

Where is the other wire from the tach connected?

In this diagram from Fords 1971 shop manual, the tach is wired between ignition-switched power and the coil’s pos post.

View attachment 83508
Is this proper? And even with a Pertronix III?
Sorry haven't been on in a while and just saw this. To get a ignition on full 12V to the coil, I ran a wire off the wiper motor red wire. I have that wire powering the electric choke and going to the + side of coil along with the tach wire and red wire from the ignitor. I then have the black wire from the ignitor going to the - side of the coil. I just added the 5 ohm resistor that Petronix suggested to get the tach to work right, but haven't run the car yet as I'm still finishing up the intake installation. I hopefully will not this weekend if that corrects the tach. If not then I'll try the 10 ohm or 15 ohm resistor
 
Sorry haven't been on in a while and just saw this. To get a ignition on full 12V to the coil, I ran a wire off the wiper motor red wire. I have that wire powering the electric choke and going to the + side of coil along with the tach wire and red wire from the ignitor. I then have the black wire from the ignitor going to the - side of the coil. I just added the 5 ohm resistor that Petronix suggested to get the tach to work right, but haven't run the car yet as I'm still finishing up the intake installation. I hopefully will not this weekend if that corrects the tach. If not then I'll try the 10 ohm or 15 ohm resistor
I'm not an expert on this, but I had the same problem with my tach under-reading, and I was told to connect NOTHING (like the choke) to the positive side of the coil. When I disconnected the choke lead from the positive side of the coil and ran it to the alternator wire my tach worked fine. Read this thread: https://7173mustangs.com/threads/factory-tach-inop.39245/
 
Thanks for sending that link. I wanted to use the throttle position selonoid wire for 12v, but when the car was restored several years ago, someone wired the headights to this wire, so it only is energized when the headlight switch is on. I haven't tried to correct that yet. I may need to rethink the wiring. I hope to have it running this weekend and will check everything out then.
 
Following up on this. I tried adding 5 ohm then 10 ohm then 15 ohm resistors to my tach wire as Petronix suggested to get my factory tach to work correctly and nothing worked. I then watched a video my Auto Resto Mod and followed the instructions for adding a trailer wire extension harness behind the tach and now the tach works with my Pretronix II.

1707519921145.png
 

Latest posts

Back
Top