Air should be able to flow through the standpipe freely in both directions. It's simply a baffled tube that prevents splashed oil from the crankcase from getting sucked into the intake by the manifold vacuum. The "valve" in your photo appears to be simply a calibrated vacuum leak, not a true PCV valve. It would draw a small constant air flow through the crankcase and into the intake, purging blowby and water vapor without severely affecting manifold vacuum. Later valves had a pulsating flow caused by a spring-loaded shuttle valve that reacted to intake pulses to take small sips of air from the crankcase. If that's the original equipment valve, just clean it thoroughly and reinstall it. It should work OK. I'd suggest giving the standpipe a vigorous cleaning with something like a strong solution of Trisodium Phosphate and hot water, followed by flushing with a pressure washer. The crud that comes out of a well-used standpipe or a road draft tube is pretty impressive! Back in the dark ages, we would fill one with gasoline, light it off, and let it burn for a while, and then shake the soot out of it.
Jerry

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