Disc Brake Conversion Failing

Would a car without a proportioning valve run a larger resivor to increase line pressure to the front? Totally Spitballin' here. Just wondering.... but yes, these people MAKE mistakes, and even sell crap that dont work. Knowingly....
**** if I know. I'd never try it. Brakes are one thing I want right. You hear what I'm sayin? lol