Moroso Two-Piece Billet Aluminum Valve Covers with Oilers are designed with a valve spring oiler built into the lower rail of each cover. The spring oiler feature enables you to check or adjust rocker valve clearance without removing the valve cover.. Moroso's billet valve covers with oilers contain multiple oil supply ports and are made to clear shaft rockers. These durable 2-piece valve covers have a black anodized finish and are sold in pairs.