Guys i have a ZC sohc non vtec head, I put high comp pistons a few months ago just a couple weeks ago took her to the drag strip everything when well but a valve floated!!!

Chamber 2 the spark plug was burning black jus within 15mins of driving (city driving) so i thought maybe i needed to change the valve seal... Opened up the headers and saw oil in the 2nd chamber aswell...

so now changed the valve seals new cylinder head gasket new sparks... but when u rev 1200rpm theres a knocking sound?? could it be that the pistons are how hitting the head???? impossible right? maybe the gasket i was using before was a little bit thicker? since they are dome pistons is it possible? i cant afford another overhual guys... ugh what a headache... or maybe i didnt assemble the rocker arm properly? when i did the tune on the rocker arm 8 10 8 on the intake and 10 on the ex its a little bit more difficult to set... Any help would be greatly aprreciated sorry for the bad english guys.

Thanks from Manila.