I have a sbc 406 with a platekit nos big shot , i lifted a ring land on #7 cyclnder bought another piston ball home cyclinder filed to fit new ring pack istalled piston. went to the track made motor pass ,changed plugs every thing look good , made a hit on a pass , pulled plugs ,#7 a little wet and black with oil on threads all other plugs looked good . swap #7 plug in #3, made another hit pass same thing on #7. My tune up is 82 square @5.25 fp what do u guys think? forgot to ad we check the head with fluid in #7 runner and no leakage.