Electronic Tach question

I have an electronic tach....and it isn't accurate and is not consistent. I waivers 500 rpm when the engine is running at a steady speed. I have an pertronix electronic ignition. Any help on this one?

I have an electronic tach....and it isn't accurate and is not consistent. I waivers 500 rpm when the engine is running at a steady speed. I have an pertronix electronic ignition. Any help on this one?


try double grounding the tach and/or a ground strap for coil or distributor. if this does not help, you may have to run your tach through a porcelian resistor.
hope this helps,
ctesla