brake issue 80 Blazer

[dubie]

The brake light has been on since we brought this truck home. The previous owner had a rear brake line blow out on him so we replaced it along with a bad front line and the master cylinder, then bled the system out. The pedal still has weak pressure and the pedal won't engage the brakes until 4" from the bottom. Would that rear brake line blow out cause and issue in the proportioning valve? If I slam on the brakes, the front ones lock up while the rear don't seem to engage. There was fluid coming out of the rear bleeders but not as much as there was up front.

Any ideas boys?

[68Timber]

Did you get it resolved? Here's a link that came to mind about the proportioning valve: http://67-72chevytrucks.com/vboard/showthread.php?t=656246

[dubie]

not resolved yet. I'm going to bring it back in tonight and check the prop. valve. I'm getting fluid out of the rear bleeders but not near as much as the front. I'm going to crack a rear bleeder and have someone depress the pedal and see if that forces fluid to the line. It has the stock Prop valve in it so I'm not sure if it has the bleeder pin