BMN head question

guys can any one tell me can the rocker arm shaft be removed without messing anything up timing wise a I have. Levy head gasket (oil leak) and iv noticed my cars had a replacement he'd t some point in its life so I'd like to check the he'd bolts as iv convinced there not as tight s they need to be so I'd like to back them off one at a time to check them , before I go down the route of replacing the head gasket :(