HOW ACCURATE ARE THE FACTORY TACHS

I think most folks would be shocked to know their tach’s are not correct, at probably several different RPM ranges.

I have a tach in the shop that is off almost 200 RPM at 1100 RPM. It’s caught up at 1500 and stays that way until 8k. That’s an Autometer monster tach.

Had another Autometer in my race car, and it was off at idle by 100 RPM and about 300-400 at 8500. These aren’t cheap tachs.

I can now test a tach when I test an ignition with the tach on my distributor machine. Some of my digital Mallory ignition boxes have a tach test feature as well.

It’s another thing that should be tested, because if the tach is wrong, it changes things.