Whats the deal with 260 tach's going bonkers

[jesusno2]

my tach in this 260 i just picked up just goes haywire, it never reads correct most the time it just stays pegged at 8k. I'm new to Z car stuff so im like a sponge right now learning all i can.

[datzenmike]

Clean and gap the points. My '70 Dart would have a jumpy tach when the points were worn. You could also look for a loose connection on the coil and the ballast resistor.

[jesusno2]

Clean and gap the points. My '70 Dart would have a jumpy tach when the points were worn. You could also look for a loose connection on the coil and the ballast resistor.

 

well mike its got a electronic ignition. It looks aftermarket im guessing, but still has a ballast resistor?? I'm still sorta z car retarded

[Ranman72]

well mike its got a electronic ignition. It looks aftermarket im guessing, but still has a ballast resistor?? I'm still sorta z car retarded

probably petronix

maybee a grounding issue

[ggzilla]

280Z had electronic ignition with twin-ballast resistor (three terminal resistor). Only the 1978 had no ballast resistor. They had an aluminum box with 5 or 6 screw-on wire connections.

I think 260Z had this also

 

The coil might be wired incorrecty, that can make a tachometer jump and have a rough idle, but still make great power once it gets going.

[jesusno2]

Well it runs like crap at idle to about 1500. I,LLC take a picture it looks all stock to me

[ggzilla]

I had this same problem coming home from Canby, where I swapped a distributor and coil. When I got home I changed the coil and all the problems went away. Funny too because at the drags, i had really good top speed.

 

I think the problem was how the coil was wired. There is an extra wire in my harness which I didn't hook back up. but maybe that coil was bad. Since I had an extra, i swapped it in. I should have tested it with an ohmmeter.

[jesusno2]

pics of the coil and resistor

wire that goes no where