I think there is some confusion here between 12v and 24v VR engines. On a 12v, the cams work like any traditional 12v V6 engine - one looks after inlet and exhaust for 1,3,5 and the other inlet and exhaust for 2,4,6. On the 24v, one camshaft does inlet and the other exhaust, using a rather trick bit of head design. This website explains it pretty well: http://www.autozine.org/technical_school/engine/tech_engine_packaging.htm