200 300 m valve hitting cylinders

I got a 2000 300m and for some reason I keep getting a knocking sound on the right side. I took the timing covers off checked timing and everything is good there. so checked cams and found nicks in cams. so I went to a pull apart and pulled a cam and rocker for each side and put new lifters in the rocker arms. Put it back together and made sure it is in time. Started it up still making the sound so when I investigated further I found that the valves on cylinder 4 were hitting the top of the piston. Not sure why it is doing this. I made sure the cams and the rockers matched. Could the camshaft sensor cause this. Any ideas please let me know. I even tried advancing and retarding the timing by a tooth to try it out. At a loss Please Help...