Set your cam upright on something flat (glass, parallel block, etc). We slide a trued sleeve (which is slightly longer than the down end of cam) over the end that's down since some cams may be a bit irregular on the end or have a burr around the center. Zero Out the indicator on the thrust washer surface of your old cam, then set up your new cam to see the difference (+ or -) in length of your new cam. Assuming your old cam was installed with the correct end play, this method can eliminate having to remove a tappet block to check cam end-play ? Another more accurate method to check lengths of parts more precise than just using a caliper.
Posted by Noot