[masterhussey]

I did search the forum and didn't see anything.
1974 SD. that runs very well. Rev's nicely, def has power. Its a single points distributor factory. yes I know i could just put a new one in or convert it to the petronix (going to do the petronix later, I just want the tach to work correctly first)
Need some help: My tach is very jumpy not the motor, motor sounds amazing, idols perfect. So here are the things I found wrong, and tried.
1. I found the lead from the distributor cut and spliced back together. It was done terribly. So i replaced the lead with a new one.
2. I disconnected the factory tach and hooked up a different tach and it is the same issue. I even fully disconnected the factory tach when testing the aftermarket one so that eliminates the actual gauge.
3. It is a new coil, I tried a different coil and it was the same thing.
4. I'm going to replace the condenser tomorrow so i'm not sure that will fix it.
5. I did have a loose ground from the head to the firewall so i cleaned and tightened that up.
6. the points, cap & rotor appear to be in good shape.
I know its probably something stupid so what am I missing? i'm starting to get stumped. so all ideas welcome. I would like to keep the original one in there.