68 L-78

[rts]

My question is when driving the car I notice that the tachometer is incorrect and looks like its reading half the RPM it should be, is there a calibration or is the tach just need to be rebuilt??
When the car is idling its at 850, car has 4.56 original rear in it and theres no way at 60 the car is taching 2000, I also check the speedo and is close to MPH with another car on highway!!

Any thoughts would be appreciated

Thanks

[cook_dw]

Is this a factory tach or aftermarket?  First thing I would do is wire up another tach and see if you get the same or different reading.

[rts]

Its a factory set up

[bcmiller]

Assuming you have an in dash original tach, yes the first thing I would do is find an aftermarket Sun tach and mount it on the column.  Then see what that shows.

With 4.56 gears you should be near 3500 in 4th gear (based on a 26 inch tall tire).

[rts]

Ok
I will try that this week end

Thank u