its a trition. its a chain drive motor. chances are the "new" engine is bad. the only thing that going to stop the rotation is a rod. probly number 8 cyl. unless one of the 2 chains broke. Witch i doubt., but in the case that you didnt break a rod, and you broke the chains, then you bent a valve or 2. Do a compression check, If it fails pull the motor.

Possible a bent or stuck valve that's not allowing it to do full rotation

You said rotates easy? Like it has no compression? Coul be jammed rod are stuck piston

sounds like a broken connecting rod another way to say it is its junk sorry

Just changed my engine on my 2005 ford e250 5.4l v8 - the engine cranked over 3 times at first then it stopped. i cranked it by hand and it cranks very easily but then stops after 95% of the rotation. what could this be? do i have to replace the engine or is it fixable? i can crank the engine back and forth but it'll stop after 95% of the rotation