Pertronix Tach Issue

[jpc3006]

EastCoast, I just noticed your post.

FYI, I eliminated the distributor points in my 1973 Z this past spring and am running the same setup as you (Pertronix Ignitor II with a Flamethrower II 0.6 Ohm coil) and have had no problems. I believe the installation of the Pertronix Ignitor II with a Flamethrower II 0.6 Ohm coil has smoothed out the idle a bit and the engine pulls strong to 6000+ rpm. 

As part of my installation testing, I did run in multiple configurations: 1) the Pertronix II with the stock ballast resistor and stock Nissan coil, 2) Pertronix II with the stock coil and no ballast resistor, 3) Pertronix II with 0.6 Ohm Pertronix coil and ballast resistor, and 4) the final configuration of Pertronix II with the 0.6 Ohm coil and no ballast resistor. In all four configurations my tach operated correctly. I did this because I was concerned that higher current in the ignition circuit might cause problems with the tach. I even took  video of the speedometer and tach at various engine speeds for each configuration to verify that the readings were consistent.

If you want to run the Pertronix II and 0.6 Ohm coil w/o a resistor, my recommendation would be to try the mod that Zed Head described above, if that doesn't work I'd be looking for another tach.

[eastcoastz]

@jpc3006 Thanks for the info!  I ended up going back with the 0.6 Ohm Flamethrower II coil with a 2.4 Ohm ballast resistor.  Knock on wood, the tach is been working well with that setup.  The ballast resistor is part F1104 if anyone needs it in the future.

[Zed Head]

The Pertronix II is current-limiting.  Maximum spark energy.  The ballast resistor takes it back down close to Pertronix I level.  Probably between I and II.  Just saying.  

Let it ride as-is and if you ever get the tach out think about trying the modification.  Can't blame you for not being eager to take the tach out.  It's a PITA.

If it was mine I'd probably reach up under the dash and just pull that wire a little farther away and see what happens.  I think that the point of the adjustment is to reduce the magnetic field.  Might be enough to just bend the wire.

Edited November 16, 2022 by Zed Head
Th > The