I've seen it done on a 2.6 head, and it ran for 100K. Cut out the valve seats, heated it at 500 in the oven overnight in a jig to reduce the warp and straighten the cam bore, and welded it the next day while still hot. The welder was an artist with the TIG. Almost didn't have to grind the weld smooth. No fix, no pay warranty, and they'd give me a new core if it failed, so I tried it. I liked it. $150 to do it. He ground it out and just built it back up. Magic stuff...

Not responsible for advice not taken...