doggitter

Mike, I ran across a thing last night that would fix you right up. One of the major cam grinders, seems like Isky, offers a cutter that replaces the valve head. Install a shank and turn it into the piston, cutting a pocket as it goes. If you degree when the piston needs clearancing you can take care of it. I'm sure they'll provide instructions too.

Hope this made sense to you, looks like it may be confusing. It's a cutter that, with the shank attached, fit's in place of the valve. that way it will cut to the correct angle and position. Depth will be up to you. :>)