That is a good point Jerry. But no I still ain't buyin your Dyno! ;)
Here is the way that Sam Bell from Motor's Testing Facility put it...
As you might expect, blowby gases are produced in varying amounts under different operating conditions. At idle, when manifold vacuum levels are high and loads are low, crankcase fumes are at a relative minimum. Under these conditions, the high vacuum sucks the restrictor to nearly close the valve. Makeup air is supplied to the crankcase via the filtered breather cap, or breather hose, “positively” displacing the crankcase fumes.
Under midrange throttle openings, engine loads and speeds are higher, and more blowby gases are produced. Manifold vacuum, however, is lower, so the spring tension can largely counterbalance the pressure differential, thus allowing increased flow through the valve. As before, the breather supplies clean air to displace the fumes.
At very high throttle openings, intake manifold vacuum drops to near zero. Spring tension then holds the valve open for maximum flow, just as it does with the engine off. Even so, the amount of blowby gases needing evacuation often exceeds the flow capacity under high-load conditions. At such times, a substantial portion of crankcase gases may flow backwards from the engine through the breather and into the air filter housing. (This accounts for all those oily breather filter elements we changed back in the not-so-good old days of carburetion.)
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Since we are talking about the good old days of carburetion, the engine shops advice, as well as various web sites out there, not to mention a few of our own StoveBolters, have suggested that 1 to 3 inches of mercury at a stable Idle will be the best compromise and is the accepted industry standard.
To further complicate matters, these engines weren't designed for PCV and the engineers felt that a 1-1/4" HOLE was sufficient! Since the PCV Valves I am using have the industry standard size, we can assume the manufacturers through what they call flow testing, can make a positive vac pull on a 3/4" hole. 1 to 3 inches at a stable idle accomplishes this. Of the 20 or so inches present in manifold vac pressure, this Valve pulls 2 (or about 10%).
To answer your question Jerry... I rely on other experts so I have to go with JUST FINE.
