Well, i went to a machine to get my a6 head resurface only. And before you know it. I went to pick up the a6 head and the guys there hot tanked the head without taking the cams, rocker arms, etc off. I was wondering since i saw some rust, if it would cause the cam to be stuck. I tried turning the cam gear by hand but it wont moved. I even tried using a piece of rod to move the cam gear. It wont moved at all. Well before taking the head to the machine shop. The car overheated and so i had to remove the head to get to the head gasket. I also have a z6 head that i tried turning by hand. It turns so easily. So what can cause this? What should i do?