in theory slpr teg, you are right, but there is a lot of "overlap" between the strokes. Do no confuse this with overlap in which the intake and exhaust valves are both open. The intake valve actually opens 15* before the actual intake stroke begins and stays open 40* into the exhaust stroke. With the pistons comming up fast than the valves closing this will put a strain on the valve train if there is water in the way