I've got my head in the shop now (250 head for my 200 block). Anyway he said to install larger valves he would have to put in larger valve seats. He also said that it would take away to much metal, making it too thin. My question is, will CI's larger valves fit? The stems are 5/16", isn't that stock? He was unaware of these valves, and said the head is fine other wise. I'm taking him info tomorrow. Hope I worded this OK.