2.6L 12 Valve SIHC 3 Valve Hydrolic adjuster including jet valve. The third valve or jet valve is used to send a rich fuel mixture to the spark plug. The spark plug fires easily in the rich fuel there by firing the lean fuel from the main carburetor. If you have not changed the carburetor you should stay with the (jet valve, lean burn, statisfid charged ) all the same thing, different names, for the 3 valve head. Putting on a 2 valve head will shut off the rich fuel and the engine will run lean.