Valve Overlap 🚗💨🔧🛠️👇 Valve overlap is an important concept in internal combustion engines that plays a major role in engine breathing, efficiency, and performance. It refers to the short period during which both the intake valve and the exhaust valve remain open at the same time at the end of the exhaust stroke and the beginning of the intake stroke. In a four-stroke engine, the exhaust stroke pushes burnt gases out of the cylinder. Just before this stroke ends, the intake valve starts to o