My husbands 2005 GMC, 5.3 ls motor. He pulled it out to replace the mains, bearing, crank, and caps. He put it all together right and the motor turns fine. This is the second time this has happened. He sets the motor in the truck and starts putting it back together then when he trys to turn it to put the torque converter bolts in, the motor won't move an inch. Tried with a bar on the crank bolt thingy and it won't move. The tries with the pully, the pully will move but i was under it when he was doing this and nothing was moving. He is so mad cause he can't figure out what he had done wrong. IT doesn't make much since that before it gets set in the truck it turns then once in place, it won't. Any ideas???? Thanks so much in advance!!