Never underestimate any part of the engine to replace
Engine valves are mechanical components used in internal combustion engines to allow or restrict the flow of fluid or gas to and from the combustion chambers or cylinders while the engine is running. Functionally they behave similarly to many other types of valves in that they block or pass flow.
The term engine valve can also refer to a type of check valve used for air injection as part of emissions control and exhaust gas recirculation systems in vehicles. First of all, make sure which tubes you need.
Engine valves are common to many types of combustion engines, regardless of whether they run on a fuel such as gasoline, diesel, kerosene, natural gas (LNG), or propane (LP). Engine types vary based on the number of cylinders which are the combustion chambers that generate power from the ignition of the fuel. They also vary according to the type of operation (2-stroke or 4-stroke) and the design positioning of the valves within the engine.
Valves: what they are for
Four-stroke internal combustion engines use two main types of valves: the intake valve and the exhaust valve. The intake valves are opened to allow an air / fuel mixture to flow into the engine cylinders prior to compression and ignition, while the exhaust valves open to allow exhaust gases to be expelled from the combustion process after ignition occurs.