2002 Avalannche 1500 5.3L locks up on start
Last time I drove the avi, I parked it for a week and then tried to start it. The engine turned over for a sec and locked up, while running the starter. Makes the electrical system go dark in a hurry. Took a breaker bar and socket to the crankshaft bolt in the CW direction and could not budge it. When reversing direction, it would turn. I turned it 180 degrees and then tried to start it again, with the same initial results. Always stops at the same angle. Thought maybe that the timing chain had broken and wrapped around the crankshaft an jammed it .Towed it into my garage and removed parts on front of engine to the front cover and the timing chain is intact. Attempted to turn crankshaft again and it turn s freely with no stopping. Had take plugs out and stuck a fiber optic camera into each one to see if maybe a valve had dropped into one cylinder. Everything clean there. Don't know where to go from here.My dad is a fanatic Ford guy and says I should take it to the boneyard, but I would have expected nothing less from him. LOL. He is 92 yrs and a Ford lifer. Anyway, I would appreciate some help and not a tongue lashing.