These valve covers start life as a 36lb hunk of 6061 aluminum, and after many hours of machine time on our in-house Okuma machining center, they come out like this. You don’t have to be shy about tightening down these like the stock cast pieces. You can tighten them down as much as you want as long as you don’t snap the bolts off in the head! The streamlined profile of these covers allows us to place the baffled -10AN ORB breather ports right on top of the valve cover for maximum flexibility in routing of breather lines. The -20AN oil caps ensures that leaky oil caps will not be an issue anymore.