Tachometer Calibration

[dprice]

Following up on a earlier post, I hand checked the engine speed using a portable Tach and found it to be off.

Engine Tach showing 1500 RPM and the handheld showing 2000 RPM.

My Tach only has a 4 position Dip Switch not the more common 15 switch so I had Teleflex Fax me the setup sheet.

Now for the stupid question.

How do I know how may poles my alternator has ?  This information together with the pulley ration is used to adjust the dip switch.

The only information I currently have written down on the Alternator is:

51A Motorola (Prestolite)