Unless you have a closed system style breather element (with the breather filter in the air cleaner housing) you will have crankcase pressure at WOT blowing oil out the valve cover breather. At WOT, there is no vacuum, making the PCV valve useless. Without the PCV valve creating vacuum in the crankcase, the pressure builds and blows oil vapor out any opening (i.e. the breather). A properly plumbed engine should have a PCV valve in one valve cover (or the valley pan) going to a combined vacuum source (i.e. rear of carb) and a breather tube from the other valve cover going to the air cleaner housing with a respective breather filter. This will allow the oil vapor to be sucked down the carb at WOT and burn the oil vapor/fumes, rather than spraying all over the valve cover.
|