Measuring To See Which Crank Trigger Is Right For Your Engine

Last Updated: 11/01/2007

This article covers how to measure your crankshaft pulley in order to fit it with a universal 36-1 trigger wheel. There are a total of five measurements at most that you will need to make to determine what parts you will need to order to fit your engine. If you have a flat crank pulley, you will only need to know the outer diameter of the pulley, the center bolt diameter, and the length you will need for the center bolt.  Dished pulleys are a bit more complicated; we recommend using our trigger wheel spacers to mount a trigger wheel on such engines.

For a dished pulley, you’ll need two additional measurements. One is the distance from the front of the pulley to the mounting face.  The other is the maximum diameter that will clear the bolts holding the pulley to the damper (if used) or the shoulder of the pulley (if it is held on by a single center bolt.  The spacers are 0.25″ thick, and you’ll need enough to make sure the trigger wheel is supported by the spacers instead of the edge of the pulley.


Here are two pictures of measuring the outer diameter of a pulley and the required length of the center bolt. In this case a calipers has a depth probe that is running from the front of a trigger wheel to the bottom of the crank bolt hole.

The spacers and trigger wheels all have a 1/2″ center hole. This will need to be drilled out to the crank pulley diameter.

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