If you have a valve cover with no vent pipe, and you want to install the 1/2-inch vent hose from valve cover to air cleaner, then you need to drill a hole in the valve cover to accept a vent adapter fitting. The one pictured here was originally intended for valve covers on Volks Wagon air cooled engines. It is made by Empi (part number 9164), has a JK Part Number J18151 (www.justkampers.com), and is commonly sold with two pieces in a bubble pack. The same part can also be used to add a vent port to an air cleaner housing.