We may be at cross purposes here, possibly my fault for quoting you. I wasn't suggesting that skimming the head face will soften it, simply that seriously overheating the cylinder head will soften it - how else would the head warp/bow?

I was also under the impression that if the head is overheated too much, then the head could be basically scrap, as the material properties could change (regardless of bowing/running out of true). I can't recall where I got this info' from (which may render my comments useless , but it is something I remembered - if not the specific details), and so yes I could be wrong. If you or someone else knows different, then I'm happy to be better advised

I don't know the makeup of the cylinder head material, the Cosworth web site used to have a lot of info' on the casting processes etc. but it's all pretty much gone after successive buyouts and redesigns of the website and the company's change in focus. Again, my memory of this is that it was Cosworth's superior casting techniques that made them such a good head for a production engine, not necessarily the materials used.