Datsun Roadster Forum-311s.org

So I’m assuming that the left tach is a 1600 and right one is a 68 exclusive 2.0. The big number increments do not match the positions on face due to rear ended ratios 3.70 vs3.90. But did the 1.6 tach ever come without a 0 position pin stop? The face at 0 mile on left looks to never have had one. But it does rest where it is on left way below 0 mile mark. My original 2.0 doesn’t have a 0 stop pin either. Curious.

The white faced gauge is a repainted 2L. The bottom gauge in the right photo is a 1600 (only goes to 7K) and the upper one is a 2L.

Will

Differential ratios do not affect engine rpm at tachometer. On our cars it's measured off a cable attached to the distributor.

Well, that’s what I originally thought but the locations of speed increments are positioned differently on the 2 tachs. If I swapped between the 2 tachs the speed indication would be different no? Also my biggest curiosity was the 1600 without a 0 mile stop pin. There isn’t one and the needle sits way down by turn signal lt. is this normal on some 1600s. Or should they all have a 0 mile stop pin?

Someone should know! I do not though. It would be possible to test both tachs and compare them to a service tach or timing light that shows rpms.

I think you mean 0 RPM not 0 MILE when referring to a tachometer.

The tachometer’s internal gearing is probably different so the seeep can take up the same number of degrees on the face. They should work correctly for either engine.

Calibration is exactly the same on both units. (You can put a 7K tach into a car that had an 8K tach or vice versa and it would read correctly)
There should be a pin in the dial for zero indication so the unit you are showing probably has a broken pin. Calibration would likely still be good but unless the tach had a major failure where the pointer spun around and broke the pointer.

Jon

Only the speedometer/odometer is affected by variances in wheels, tires, differential etc.