[72z240]

Just got my tach working, the wiring was wrong when I got it. But the tach is not reading accurately at all. I am using an MSD 5 ignition and a Mallory Voltmaster coil on my 72 240z. Is it possible that the high-voltage coil is throwing off the tach? And what can I do to correct it? It has been pointed out that I may be able to adjust it with the rheostat in the tach itself. I don't see a ballast resistor of any kind, do I need one? I think originally the Voltmaster coil came with a resistor.

Thanks,
Kurt

 

[DRT240]

I had a similar problem a couple of years ago on my 72 240Z. I have a Crane XR3000 electronic ignition coupled with a Crane Hiperformance coil (FS60). There is a resistor somewhere in the wiring between the coil and the tachometer (I spent many hours looking for it and could not find it) - the original coil did not come with a resistor. The new coil had a resistor built in and the tach couldn't handle the two resistors. I put a jumper wire at the tach bypassing the original resistor and now it works great.

 

[JJs72]

I have the same MSD set-up as you do and you need to get the MSD tach adaptor unit. It will work just fine after you spend some more money...

 

[72z240]

Looks like there are two tach adapters available. One is for models which originally have a ballast resistor, the other is for those which do not. I can't find the ballast anywhere, but is this the one I need? PN8910? or PN8910EIS?

-Kurt

 

[72z240]

Ok, think I got it. The 8910 is for point triggering and 8920 is for magnetic triggering. I just ordered the 8910 for my single point dizzy. Hope it works!