Why AMS recommends Race balance shafts

In our experience using a stub shaft when removing balance shafts can increase the chances of oil pump failures. This can be caused by the lack of support provided by the rear bearing on the original balance shaft. The support is needed to prevent the oil pump gears from pushing apart and wearing into the aluminum pump housing. Once the process begins the gears can continue and wear enough to cause them to seize. During this whole process the aluminum that is being worn away can enter the clean oil stream and contaminate engine bearings and other components causing them to wear prematurely.

To help prevent this process we have come up with a way to support the oil pump gears and still remove the rotating mass. We start with a stock balance shaft then, spin it in a lathe to make sure there is no radial run out. This ensures that the shaft will spin true in the bore and not cause premature bearing wear. We then machine the weights and extra material off in a precision lathe and re measure run out to verify nothing changed during the machining process. All parts get cleaned thoroughly and are ready for installation. In the pictures below you will see the differences in the three shafts available. There are also substantial weight differences in the three shafts as seen below.