In article , John Roncallo
writes:

Is there any text book way to check this. Our FBO seems to feel that
calibrating the Tach is a big deal. I'm currently thinking of just
replacing the Tach without tring to calibrate. Right now it looks to me
as if we just replaced and engine at 1700 hr thinking it had 2000 hr.


I got a free program that uses the engine sound to give you RPM. I don't know
the web site but the program says email is . Just
take a laptop to the plane and check it out.

Chuck