here's a view of what can happen after cracks appear: the valve seat inserts can come out. This is definitely not good.

Look at the gap between the bottom of the inserts and the casting. The exhaust seat has moved further than the intake insert; but both have moved. There are two fine cracks between the inserts. I tried to get a decent pic of the cracks; but my skills will have get a lot better before I will be able to capture such delicate detail with a camera.

Yes, this head is junk also.

UPDATE: As these heads become less common, it will become necessary to try to repair a head like this one. Not exactly an easy repair, but it could be saved.