I bough a core stock 5.7 hemi that did the same thing. It sheared the cam key and bent the valves. Upon disassembly I noticed that the front cam bearing had turned approximately 90* in the block. The cam had tried to seize to the cam bearing. All of the other bearings looked ok though, including the rods and mains. It is my understanding that this is common with these engines. You might consider popping the cam out if you haven't pulled it out already. Inspect the cam journals and also check to see if the bearings line up with the oil holes.