Mitsubishi Repair: Engine repair, combustion chamber, clunk

Question
I have a 1.5L SOHC engine. I recently had to replace the timing belt. All timing marks OK. When I went to start the car, it tried to start but did not turn over. Tried to start again, and when I did the engine made a "clunk" and wouldn't even try to start. So I rechecked the timing TDC, etc and upon further inspection found that my 2 spark plug (from crankshaft) had been broke off in combustion chamber. I am assuming I had valve interference. So after fishing the broken piece out with a magnet, I replaced the plug.(NOTE:I could turn the crankshaft in both directions halfway but not a complete turn) So I tried again. It was turning over a few times and the last time I tried it, it stopped again. First thing I did was checked that same plug and sure enough same thing happened just pushed the tip of the plug inside itself instead of breaking off. Could you tell me if I will need to take apart the cam and all and what to replace? I have a manual, but I am not sure if I should do a complete overhaul. Any ideas?

Answer
Jackie,
the piston should never reach the tip of the spark plug.  It sounds like you have a bent valve that hitting into plug and bending/breaking it.  You might have luck simply replacing the 2 valves on the cylinder where you're seeing the problem, else be safe and replace all 8 valves.  However, this does require removing the cylinder head.
Good luck!