Fan Hub Working Height

The Fan Hub Working Height is the measure between the block mating surface and the hub where the pulley bolts.  Matching up this distance assures that your pulleys align.  If you find a variance, your may require a spacer or shim to maintain alignment.  These are available at parts stores and catalog distributors.

Chevrolet was consistent with a "short" pump measuring 5-5/8".  Corvette "short pump can be 5-3/4".  A Chevrolet or GM "Long" pump is less consistent and could be 6-7/8", 6-15/16" or even 7".

Other companies are the height they were designed to be and there are no steadfast rules.