You can't lap out a chip, you'll just ruin the new valve trying. Does the new valve have the same seat angle as the valve seat? I see you are in Melbourne. I live in Melbourne and have a set of Warren & Brown cutters that I inherited ten years ago and have never had occasion to use - I haven't worked on valve seats in more than 30 years. I don't know whether I would have the right seat angle, let alone the right pilot diameter. If you can find out what both of those should be, I'll see if I have them.
