You are confusing this. CC'ing is just a matter of checking the volume of the cylinder head. It's something that you really should do to make sure that your compression is OK. How deep you set your valves in the head, how much you shave off the surface and what kind of spark plugs you use, all contribute to the volume of the head. It's a number any good engine builder should know and provde. It's a result of modifications, not a modification itself.