This is regarding the Predator Hemi engine only...
The crank shafts in the Hemi engines have a more rounded look to the top of the journal unlike the other Predator or Clone cranks do. This causes a problem when using high duration cams like the Mod2 or F275. The lobe of the cam will hit the high rounded spots on the top of the crank. Easy fix here. Just wrap some tape around the crank journal and grind the top part of the crank flat. I use a standard bench grinder to do this (but can be done with other handheld grinders). Grind the top part of the crank down enough to allow the cam to clear the crank. It doesn't have to be ground all the way down to the journal but needs to be ground more than half way down. Then you can use some fine sand paper to clean up the area you removed material.
Grinding this little amount will not unbalance the crank because the crank is not balanced to begin with. Also this will not make the crank weaker in this area. If you have any further questions feel free to call us at 800-521-3560.