If the camshaft snapped on a Nissan Serena could that have caused damage to the valves?

i think u mean cambelt not shaft as i cant see that snapping. Though the answer for both is the same yea it will damge the valve's and pistons this is because the cam will stop and the crank will keep on goin.This means pistons will meet valves at speed (not good) sometimes on petrol engines there is enough clearance so the 2 wont meet but u dont stand a chance on a diesel.