1984 honda magna v-30 cam shaft issue anyone know motors?

I have the cam lined up,and all others in their spot. but the last one is giving me problems. When I put the cam holders on, and tighten them down, I can only rotate the motor almost 180 degrees but not quite.
When I loosen the cam holder it turns freely, What can be causing this issue. I have recently replaced a valve rocker arm, but totally stumped. never have I seen this problem before.
 
Back
Top