Crankcase ventilation with blow through supercharger

inertia said

As soon as manifold pressure went positive of crankcase, the PCV valve would close, as it would with a backfire, thus not exploding the crankcase.

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Correct, but two of my own observations;
1. Most normal pcv valves don’t seal for **** under positive pressure so it still pressurizes the crankcase somewhat.
2. The breather that normally flows into the crankcase is now trying to evacuate pressure that gets past the rings and is normally too small to do that efficiently.

Like I said vent both valve covers to a catch can with big hoses and a big filter. This is THE best way to get it done. Ask me how I know.