Yep, did mine the hard way... Took it off, had it alloy welded flush then started again. Rethreaded and a new plug. My father always said to use a copper washer too. He would always heat it in boiling water then chill it straight away in cold water. Something about it softens it up so it gets a better bite when you tighten it... Bah! Who understands old man mechanics?!!