[fiberglasscivic]

Have you done a physical inspection of the motor to see if you threw a rod or something through the block? Look around the front and rear of the lower half of the block. Make sure to look BEHIND the exaust manifold because it could be hiding something. Your going to be looking for a hole of some sort and metal chunks. Also, what does your engine sound like when you try to crank it. Don't go and try to crank it again because that could do futher damage. Just a more detailed description of what you heard. I know this sounds obvious as well but did you drain the oil when you changed the head, and if so did you remember to replace it?