Thats a bad place for a crack. However, is it a crack or a scratch? You are at the point that you need a professional, and if you know anyone who can use NDT methods to test, either zyglo or magnaflux, it would be a good time to look them up. If you don't know anyone who does that, look in the phone book for a good automotive machine shop.
A chamber sleeve might be possible. Kirk Merrington, or Briley's would need to take a look.
That sucks. Tight emptys might be a good indication of a crack in a critical area.
If you like your face as it is, maybe don't shoot it too much anymore, until you have some hard answers.
Best,
Ted
