Sound to me like there are some clearances that were set too tight. Bearings, wrist pins, ring gaps??? As said pull all the plugs then squirt in not more than a teaspoon of ATF in each cylinder, try turning over by hand with a breaker bar with the plugs still out. If it soon becomes easier to turn I'd guess rings. Never seen a spun cam bearing, but plenty of mains and rod bearings where the wrong size bearings were used. The engine builder should have turned over the engine a number of times while still a short block. It should not have been very tight at that stage. 10 sec is awfully quick for an engine to seize up. I worked at a car dealership some years ago, and a new car came in from the factory with what sounded like a rod knock. The service mgr confered with the zone rep and they decided that the engine should be replaced before the car was offered for sale, but to be sure the factory agreed it was decided the engine should be seized up, not just making a bit of a noise. Another of the mechanics was ordered to seize the engine. He drained the oil and water completely and drove the car out to the back lot where he set a weight on the gas pedal to about 1/2 throttle. The rest of us immediately placed bets on how long it would last. You know that over 45 minutes later he drove that same car back into the service bay! It was smoking like a chimney and squealing like a baby pig, but it was still running!

 

Amen to what Ax said, it is amazing how much abuse these things can actually take.