Valve overlap is the period (measured in degrees of crankshaft rotation) when both the intake valve and the exhaust valve are open at the same time.

This happens at the end of the exhaust stroke and the beginning of the intake stroke, around top dead center (TDC)

Valve overlap is intentional and helps improve engine performance:

Better cylinder scavenging

As exhaust gases rush out, they help pull fresh air–fuel mixture into the cylinder. This is called scavenging.

Improved airflow at high RPM

At higher engine speeds, gases have momentum. Overlap allows the engine to take advantage of that momentum to fill the cylinder more efficiently.

What is an Engine Block?

The engine block, also known as the cylinder block, is the main structure of an internal combustion engine. It serves as the foundation that supports various engine components, including the cylinders, pistons, crankshaft, and camshaft. Engine blocks are typically made from materials like cast iron or aluminum alloy, chosen for their strength and ability to withstand high temperatures and pressures generated during combustion

Definition and Function

A cylinder head is a cast metal part that sits atop the engine block, covering the cylinders and forming the upper part of the combustion chamber. It plays a crucial role in sealing the combustion chamber, allowing for the efficient burning of fuel and air. The cylinder head also houses various components, including:

• Valves: Control the flow of air and exhaust gases into and out of the combustion chamber.

• Spark Plugs: Ignite the air-fuel mixture in gasoline engines.

• Fuel Injectors: Deliver fuel into the combustion chamber in modern engines.

• Coolant Passages: Help dissipate heat generated during combustion, preventing engine overheating.