Ok, I have done several searches and here is the deal. I have an 1983 Z28 (LG4). Tach revs fine from 0 to ~3000. At ~3000 the tach bounces all over. Engine seems to be reving fine. Sound very good. Just seems to be the tach. This happens under load and also in neutral. I suspect the tach filter. Is this where you guys would look? Is there a way to easily test the tach filter?

I have read that you can bypass the tach filter temporarily, but I sure don't want to fry my tach by reving the engine and no filter.

I have also seen a post about replacing a capacitor on the back of the tach. But I think that is for car that are built after 1989.

thanks for you feedback,
phil