I don't know if a valve stuck wide open would strike the piston or not. I can tell you that a valve stuck closed will bend a pushrod (don't ask me how I found that out
). The head is actually pretty easy to remove. You will need to get some help to lift the boat anchor off of the block. From there you can check the valves, pistons and cylinders.
As for certain cylinders running rich I would suspect the plug wires, cap, rotor, or plugs themselves. Unless there is a blockage in the intake manifold, the gas distribution between the cylinders should be relatively equal. Good luck.
