If you're looking for supreme accuracy then you need to buy a really expensive shop tacho or, as I have done, go to an electronics shop and buy a tacho kit and build it up. It uses a white line painted on the pulley. I use it to check the accuracy of the dash tacho and then just use that....
Ayuh,... I'm borrowin' Bob's Snap-on digital timing light tomorrow...
I need to find me a Shop Tach, that can be read from the helm, as well as under the hatch....
