Saw my first big block cam replacement that wouldn't spin in the block back in the early 70s. Also saw a nice fresh 440 spin one cam bearing and ruin that block. Ever since, I have kept a cam laying around with the slots cut in the bearing journals. I have used it on ALL big block cam replacements for 40 years and haven't had a cam bearing problem since.

It has had to cut it's way into more than one engine, but it had always done the job. There are more precise ways to go about this, and going that way is good. But grinding the bearings into submission with a grooved cam has never presented a problem in my experience.