305 SB, getting carbon building up in #7 cylinder. Just did a head gasket job and when we pulled the heads, #7 was caked. Put about 1500 miles on it since then, checked the plugs while changing valve seals yesterday and plug in #7 was getting built up on again. I guess I will check it again in a week or so. Does this sound like a valve problem? I readjusted the valves after doing the valve seals, hoping it will improve.