Help! Valve/piston Interference after guide rail job.
Tonight I finished replacing the upper timing chain guide rails as well as the tensioner. When I removed the cam sprockets I was very careful to bind the chain to the sprocket. When I was about to put the passenger sprocket back, I noticed that the mark that aligns the cam was off about 10 deg. Since it was aligned before I rotated the cam back to where the notch lines up with the mark. I then put the sprocket back on the cam. I then wanted to hand rotate the crank a bit to see if everything was ok. I then discovered that the valve was hitting the piston. How did I go wrong and what can I do about it?