Tachometer shows wrong
I have problem in my 67 Impala 327 . I am going to install a tachometer. All very simple: plus to plus, negative to ground and signal to negative coil. And the tacho shows double revs!! Tacho have a selector for number of cylinders. All set on 8, there is only one distributor - generaly can't be more simple. I checked all cylinder selections variants on tacho . Shows different numbers of revs but never proper. I even exchanged the tacho for another one and the same problem appears. Any ideas, please???