i swapped a d16 z6 head onto my sohc zc block and now i get a slight valve knock under load situations. I had the head rebuilt before installation so all the parts are good i hope. I also just checked all the valve adjustments and timing adjustments. All is on time. I was told due to having the dohc zc pistons maybe the compression is to high for the octane we are so highly deprieved of. i also have a full msd set up with the ngk plugs. All else is good though she runs as strong as my boys b16a maybe a lil' better. very impressive for a sohc. Any info would be appreciated!!!!!