Search for 'Meaty's timing belt' video on youtube. It shows you what to do. You can access a hex bolt in the center of the cam, but you might have to remove a small cover.
Alternately, you can use GENTLE clamping from vice grips to hold the upper and low cams on the driver's side so they don't move. This is how I did it. Worked perfectly.
However, people have broken the cams due to too much pressure.
Big thread, including the person that broke the cams is here: http://legacygt.com/forums/showthread.php/timing-belt-replacement-2-5t-106809.html
Alternately, you can use GENTLE clamping from vice grips to hold the upper and low cams on the driver's side so they don't move. This is how I did it. Worked perfectly.
However, people have broken the cams due to too much pressure.
Big thread, including the person that broke the cams is here: http://legacygt.com/forums/showthread.php/timing-belt-replacement-2-5t-106809.html