Air coming through the valve cover

Understood. Since this is sort of on topic, is like to discuss the PCV setup. By no means am I an expert. I'm all ears to experience. On some race cars that I race (oval) they are breather only. What's the purpose of a PVC valve on a mild or semi strip street engine ? Not challenging, just educating myself. Once it came a hell of a rain storm while changing oil when I was 17 or so. After, I finished up my oil change. My oil change consisted of a new filter and 10 quarts...I forgot that I stopped before I drained the old oil. yeah I had some blow by all right. Brain fart, young, and in a hurry !