Bottom of lifter worn thru

The cam lobes are never in the center of the lifter bore. This causes the lifter to spin when the lobe travels under it.

If the lifter doesn't spin when first starting the motor. A lifter will never spin and will wear.

Always make sure the lifter fits smooth in the bore when installing. And never let the motor go under 2500 for the first 20 minutes to 1/2 hour.

Do not shut the motor off. so you need to make sure everything is correct before you start a new motor.

Ypou can use new lifters on a new cam but never used lifters on any cam or lobe except the lobe it was on.

Oh yeah your motor does need to come apart to be cleaned and checked for wear on other parts.

Preload is the critical factor that is most overlooked on engine assembly. Larger then factory cams have a smaller base circle. So the lobes not bigger the base circle is smaller. This then calls for a longer lifter , pushrods, or adjustable rockers. Incorrect preload will also cause premature wear.

So if you install a larger cam valve adjustment is a must , Hydraulic or solid. No getting around it. 1/2 preload for break in to keep the lifter against the lobe. You can back it off to Zero once its broke in to prevent float. Or leave it where it is.

The reason for keeping the RPMs high also is to keep the oil flowing around the lifter so it floats in the bore. and keeps spinning while the lobe takes its contour.

Sometimes cam lobes on cheap cams are not all positioned correctly and prevent spin. This is how they tell if it was a faulty cam or improper break in. Just take a measurement. Also a good reason to position and true the bores with bronze bushings.