is it misfiring? because if it not misfiring it HAS NOT bent any valves, have you taken the alternator belt off and run the engine? (as you asked about that earlier.) it will be ok to run it like that for a short time, did you have the engine running when the timing was incorrect? have you completly reassembled the engine and taken it for a run? did it drive ok?
i am trying to get as much info as poss as not being able to hear the noise it is diff to tell what it is.