View Full Version : Tach done gone cRaZy

05-31-2012, 03:13 PM
I just replaced the original tach in the '85 S/S. The PO said it never worked. The new one works but reads WAY high. Normally 6K at just on plane then burys the needle at any speeds above that. Is there a way to calibrate tachs?

05-31-2012, 03:36 PM
Make sure that it is set to the correct number of cylinders. Most automotive tachs have a switch on the back for 4, 6, or 8 cylinders.

Table Rocker
05-31-2012, 03:37 PM
Some tachs have 4-6-8 cylinder modes. You may be set up for a four. Your coil is firing twice as many times per revolution as a four cylinder's coil would. That would explain seeing double values. See if there is an adjustment on the back of your tach.

Got beat by trobins.

05-31-2012, 03:39 PM
^ X3

I bet it is set up for a 4 cylinder.

06-01-2012, 12:14 AM
Ok, I don't recall seeing an adjustment but I'll pull the cluster and check the tach again. TY-

06-05-2012, 11:50 PM
That's it!!