I'm cleaning the valves on a Y8 head I recently bought used. After searching this forum and others for some tips and experimenting on my own, I've found that soaking the valves in Seafoam does a decent job of removing or softening carbon buildup. However, there always seems to be 10% or so that won't rub off. For that, I used a brass Dremel wire wheel. On 1 valve I tried a steel wire wheel and it removed the carbon as well as what seems to be surface coating. How important is it to avoid doing this? I've seen some write-ups with photos of super shiney valves.