Tachometer calibration

[425HP409]

I found a previous thread that addresses calibrating it with an adjusting screw that is at the top rear of the tach that is covered by tape.

[leftybass209]

I can add that, I have a tach that was reading low, also HEI. I assumed the board was bad and replaced it, using a new board from Cajun Tach shop. It still reads exactly the same, and has a hangup where it will freeze.

I assume the issue is with the physical mechanism needing recalibration, not the electronics.

[425HP409]

I hooked up 3 tachs to a car with a digital timing light for a reference tach and 2 calibrated perfectly throughout the rpm range with the screw in the back. The 3rd would calibrate at idle, but read 2000 when it should have been 2500. I have 2 more to check tomorrow. ps: The test car had HEI and one of the tachs had previously been in my truck with point ignition. It read the same before calibration with both ignition sources. The tack reads ignition pulses, and doesn't care if it is HEI or Points.

[Already Gone]

Originally Posted by leftybass209

I can add that, I have a tach that was reading low, also HEI. I assumed the board was bad and replaced it, using a new board from Cajun Tach shop. It still reads exactly the same, and has a hangup where it will freeze.

I assume the issue is with the physical mechanism needing recalibration, not the electronics.

Oh goody. I have one of Cajun Tach Shops new Circuit Boards for my tach and was hoing was going to sure my not reading accuaratly problem . I am using a Petronix stock look distributor.