Factory Tach VS. Aftermarket Tach

[74Chevy74]

I installed a factory tach dash I bought, and I also left the aftermarket "autogauge" I had installed to compare the two, it seems that the stock one reads about 200 RPM's higher, and react's a bit slower than the other one, is this cause it's stock?

I read all the post's about stock tach's and how to test them, it mentioned if they were slow or stuck that they were going bad, but I just think it's slow compared to the autogauge.

Can anyone tell me what they think? Do I have a bad tach or is it just Stock VS. Aftermarket.....

[71swb4x4]

It has a lot to do with the "autogauge" being a few years old and the stock gauge being 30+ years old.
I don't think you have a bad tach. I know the 67-72's are adjustable, maybe the 73+ ones are too? The 67-72 tach's have a hole in the back with a adjuster screw inside. Maybe someone can tell you if the 73+ ones do too.

[Nolowrider]

My factory tach did the samething. I just attributed it to the factory setup being the old style points dizzy and I now have HEI. I removed the factory and went back to the aftermarket.