New motor, sounds awful?

The idea behind break-in is to properly set pre-load on installation. Start the car, get the lifters Pumped up and spinning in their bores with RPM's before they wear the lower diameter.

As the lobe comes around it causes the lifter to spin in the bore. Improper pre-load or tight lifters are a definite disaster. Polish the bores if needed

Also make sure the lobes are not centered in the bores. They must be off set to create more drag on one side to make them spin. A bad cam is not bad material it is improperly placed lobes. Cheap cams less QC. Same as Eagle parts. As long as you check your part specs before installation they're all good for use.

A loose pre-load is better then a tight one. If the pre-load is to tight the piston in the lifter will cover the oil hole and it will never pump up.