What do breathers on valve covers do?
What do breathers on valve covers do? The thought behind the breather is that you are supposed to get more fresh air flow down into the crankcase from the valve cover. This increases the cycle of oil vapor flow out of the crankcase. The added fresh air displaces the oil vapors in the crankcase with the assistance from the IM vacuum sucking it out. Does valve cover leak affect performance? Engine is running rough and causing misfires Sometimes when oil leaks from a valve cover gasket it leaks all the way down to the spark plug galley and eventually seeps...