drum brake proportioning valve

I just converted my 65 to a duel master for a 67 Dart with manual drums. But I have never herd of this 10psi for drum brakes. News to me. And I sure do not understand why you would want that. Would that not make the brakes drag? I tore apart the factory original single pot cylinder and I saw no form of check valve at all. And I know there is none in the distribution block. And the brakes worked just fine. Sounds to me like you still have air in your lines, or have a disc brake master. But I am no expert. LOL