The machine shop said they had not pressure tested the cooling passages, but they would be happy to do that. So I took the head back to them. I asked if they could tell whether the head gasket had been leaking and they said they did see a place where it looked like it had ( they said they had told me that when I first took the head to them. I have no recollection of that, but at least now I feel like we know what the problem was). After talking to my mechanic, I also told them to mill the head even though it was within 1/3000 of flat.
