"The way it is" 67'swb

[sourkraut]

it is the proportioning valve. the front and rear brake lines coming out of the master cylinder go into it. the front lines go free flow directly to the front calibers. the rear port will go to the rear brake cylinders but i can adjust the brake biast or amount of braking power the rear wheels will have. normally on these trucks with the stock proportioning valve the rear wheels will lock up before the front, this will prevent that from happening once i get it adjusted.