PCV considerations

[Roger/Sacramento]

The down side to using a PCV valve is that along with the fuel-rich blow-by gases, oil vapors are trapped in the same spaces. This means that they both get sent back into the engine to be consumed with the regular air and fuel mixture. The oil can leave residue on the back of the valves and in the combustion chamber, inhibiting flow, and generally being dirty. Many engine builders use a catch can without a valve to allow free exchange of gases to the crankcase. These catch cans aren't as environmentally friendly, since the vapors are still released into the air they help but they help keep the engine clean.

Another option is to use PCV valves, but re-introduce the crankcase vapors into the exhaust, that way, the engine is not effected by the oil contamination. It's also common for builders to incorporate a vacuum pump. This literally pulls the blow-by gases out, and increases the pressure differential between the combustion chamber and the crankcase-the result being more horsepower to the wheels.