crank case ventilation

[Michael Ghia]

In an oil crankcase breather system, there must be an outlet somewhere into the atmosphere... whether that's straight back into the carb so the gas gets burned or not. If you don't have the outlet (i.e. you use a complete sealed system) it will blow an oil seal as the pressure built up inside above 4,000 rpm is pretty great.
One way which you can help the system is to use a vacuum pump on the crankcase breathing system. If you actually pump air out of the engine crankcase, you'll find you pick up hp. It has been seen to free up 10hp on big V8's.
Racers use this all the time to great effect.
Mike Ghia