Yep, you attach a tool to the valve stem and put "lapping compund" on the valve seat, draw the valve up tight and spin until both surfaces mate perfectly. Over time your head deforms slightly and the new vavles have to be matched to insure the proper seal.

A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. Herm Albright (1876 - 1944)