It's about metals that don't like rubbing against each other.
If you have factory cast iron roller cam and swap in a billet cam, the original gear material is no longer compatible.
Swap a cast one for a cast one and you can use factory style cheaper gear.
And honestly, 3 decades of cam swapping flat tappets I've never encountered this till the last two projects I got going on with roller cams. I love to learn, and I want to inform others to save a mopar from catastrophe.
