The factory Datsun 1200 tachometer has an adjustment screw. A simple turn of the screw will raise or lower the indicated RPM. At the factory this was adjusted for a correct reading at a certaom rpm. However, as components age (in particular the capacitors) the reading may need adjustment.
Take a reading using a dedicated (accurate)
Dwell-Tachometer, and if your tachometer is off, adjust it to match.
TURN
* clockwise: to lower RPM
* anti-clockwise: raise RPM
Try turning the screw 1/8 turn, and see if the new reading is what you want. You can compare the reading by connecting a dwell/tach meter to the engine, then adjust the tachometer to read the same.
Yellow Arrow points to the adjustment screw on the back of the case
