If you page most of the way down the page, you will see a special tool that is used for placing the cams in the correct position. Believe it or not, the tool will only fit one way. If one of the cams is out 180 degrees, it won't line up properly. Many people make their own tool, but it does allow for a slight error if the tool doesn't fit tightly into the slots on the rear of the cam.
Let me know if this helps. Also, tension is a pain so be patient.