Sorry, but the pistons moving around in the crank case do not cause the crank case to "pump up" and build pressure. Sure, when a piston moves down the bore it displaces air...and if all 8 were moving down the bore at the same time, you'd create quite an air compressor. That would be a very stupid design, and amazingly enough...they figured this out way back in the beginning and designed around it ever since. As one piston moves down, another moves up, keeping the volume and pressure in the crank case constant. Yes, turbulent...but constant on average.
If this "pumping crankcase" theory was correct, every "sealed system" engine (just about every single engine built since 1980, probably even earlier) would blow the PCV out as well as the pan and intake gaskets, shoot
oil out the front and rear seals, etc. This doesn't happen, right.
The truth of the matter is, if you're building crank case pressure, it's combustion pressure coming past the rings. Sounds scary, but every engine does this to some degree, and the larger the displacement and higher the compression, the more this will occur. Newer engines leak more as well. On a 514, a single factory style breather isn't sufficient at wide-open-throttle. One or two open element breathers (as suggested) should do the job. In addition, the more breathers you put on the crank case the better. Every time you double the area of the breather path to the crank case, you cut the velocity of the air flow out the breather in half. Air velocity is what carries the
oil out of the breather.
I have a pair of -10 lines running from the valvecovers of my blown 435" bbf, and I have no crankcase pressure at WOT. It does vent some, and I do see some "fog" at fire up as well as some
oil fog at WOT. The fog at fire up is steam/moisture/condensation that goes away when the engine warms. The fog at WOT is oil vapor, combustion gasses, etc..."blow-by". With just one -10 line venting the engine, I see about 1/4 psi (data logger) at wot. With two, it's zero. I keep my eye on it...it's an early warning system in the event I were to crack a ring or damage a piston.