74 260Z Pertronix Ignition Problem with Tach...

[Datsun.David]

Hey All -
I have just installed a Pertronix igniter into my 74 260Z - which required me to retrofit the 260Z with a 240Z distributor. The car runs better than ever, but the tachometer doesn't work. If I connect the tachometer lead to the coil (-) the car dies immediately (260Z gets tach signal from (-) side). If I try to start the car with the tach wire attached to the coil, the car will not start and the spark is intermittent. I think I need to introduce some form of conditioning to the tach signal (resistor? condenser?) - but I am above my pay grade. Does anyone have any intelligent feedback to offer?

I am running a 12V coil and have removed the ballast resistor as well.

Thanks Guys...

[Bwk2000]

Sorry David, just so I understand, why did you put in a 240Z distributor? Is that something to do with Pertronix?
240/260 EI swaps I’ve seen/read about involve simply swapping to a 280ZX electronic distributor & ICU to resolve the tach issues. However, to answer your resistor question, you should have a 2.2K Ohm resistor between the tach and the (-) coil post … I can’t think of any others there . Also, if you’re using a 1.5 Ohm coil, I’d reinstall the ballast resistor as well.

[Datsun.David]

Hi Kai -
The 74 260Z has a factory EI. And, the 260Z has a tach that is triggered opposite to the 240 (neg on 260, pos on 240) Pertronix doesn't build a product specific to the 260Z, so from what I understand, guys often retrofit a 240z dizzy so that it can run the 1761 Pertronix. I looked at the 280ZX option and have the equivalent in a couple of my roadsters. They work great. I decided to go Pertronix as a function of the availability of the parts. Ultimately, this solution will work - it is just a matter of figuring out the Tach solution. The car has never run better. the consensus has been remove the ballast resistor - but I am amenable to solutions using it if there is a cohesive strategy. I am trying to avoid complete trial and error - I know there are guys with the 260Z w/ 240 dizzy, pertronix and a functioning tach... I just need to find one!!!

[Bwk2000]

David - Came across this post when I did a little looking based on your assertion that it has worked for others. Does his wiring match what you have (since you are also using a 240 dist & pertronix ignition)? Not entirely sure what he means at the end about “making a jumper to bypass the ballast resistor” … but it seems to work for him - who knows?

Maybe someone else can weigh-in with another option …

D37A14CB-006D-4B25-BC1C-80800B07F716.jpeg

[redroadster]

Does it list specs on the igniter?
On factory manu rides the igniter system it transistors 12 v to much higher 40v and high amps 3.5-5 ,Mitsubishi s then has a minute/ tiny coil at the spark plug wires top , ( I was trying to test one once and talking to tech line ...was told STOP do not proceed as its a high volt risk just replace ) so not recommended to check it with a meter

[Datsun.David]

David - Came across this post when I did a little looking based on your assertion that it has worked for others. Does his wiring match what you have (since you are also using a 240 dist & pertronix ignition)? Not entirely sure what he means at the end about “making a jumper to bypass the ballast resistor” … but it seems to work for him - who knows?

Maybe someone else can weigh-in with another option …


D37A14CB-006D-4B25-BC1C-80800B07F716.jpeg

Thanks for this Kai. But, alas, he seems to be working with a 240Z, so the wiring of the ignition circuit is totally different. Hence, my challenge. I did get some info from Pertronix that may be helpful. I will know later this afternoon. I have to try a couple of resistors and possibly a capacitor as they have suggested. I will update if I sort it out...


dw