S&S Crankcase Breather Valve For Harley Twin Cam Features: The S&S crankcase breather valve not only eliminates oil carry-over, but provides a slight increase in midrange horsepower It's easy to install when changing cams or servicing the oil pump The valve is simple but ingenious. It consists of a machined billet aluminum body which contains four steel reed valves The valve body slides over the pinion shaft and inside the pinion bearing bore, contained between the pinion bearing outer retaining ring and the oil pump The reed valve allow air and oil mist to escape from the crankcase, but does not allow them to re-enter