Car sat a cple yrs. Running now, oil full, motor tapping, why? Running 3 days.

Suspect that sitting for a couple of years may have let some deposits harden, and what you're hearing is valve clatter due to stuck hydraulic lifters. If you haven't already done it, change the oil and oil filter, and use a detergent type oil additive, like Alemite CD2, STP, or Lucas. If you're lucky, it'll quiet down after a relatively short drive.