danno 128 Report post Posted October 3, 2011 My 69 has factory power disc brakes, and the brakes distribution block seems to have a proportioning valve attached to it. The rear brake from the master cylinder goes to the top end of the distribution block, then under that it goes to a cylinder thing about 3 inches long and 1 inch in diameter. Then it comes out of this and back to the distribution block. Then the pipe to the rear brakes is under this connection on the disti block. Is this a factory disti block from 69? Is it adjustable? My rear brakes lock up too early, and I have never been able to get the front to lock on a panic stop. Thanks Quote Share this post Link to post Share on other sites
LoneWolf2U 136 Report post Posted October 3, 2011 Yes it is stock. The topedo shaped thing is the porp valve. It needs to be rebuilt if it is not controlling the rear brake action. Most likely a bad seal or broken spring. Quote Share this post Link to post Share on other sites
rockhouse66 22 Report post Posted October 3, 2011 The shop manual indicates that when the distribution valve senses a front brake failure (loss of pressure), it shuttles the piston to put full pressure to the rear brakes. Maybe your valve is in this position and explains the rear brake lockup? I think you need to determine if your distribution valve is centered (brake light switch is not activating the dash light) so you can eliminate this possible cause of your problem. Quote Share this post Link to post Share on other sites
stangs-R-me 121 Report post Posted October 4, 2011 ALSO ... If the seal on the distribution block piston is bad between the inlet & outlet chambers of the proportioning valve you will see the same (no proportioning) effect as you would if the piston is shifted towards the front brake side. I know this from experience ... had an adjustable K-H Prop Valve in place of the factory one and the distribution spool was properly centered. It made no difference whether I had the Prop Valve Screwed all the way in or out my rear brakes would lock up. Finally took the dist block apart this Summer and that seal was broken in two ... rebuilt it with a Muscle Car Research seal kit and WOW, I now finally have control of my rear brakes !! Doug Quote Share this post Link to post Share on other sites
Lemon Owner 11 Report post Posted October 4, 2011 (edited) Correct me if I am wrong but the torpedo like thingy is a valve that is supposed to sense panic braking. When you stomp on the brakes the weight carries forward and lifts off the rear end causing the back to become much lighter. That thingy slows the sudden pressure to the back brakes with a spring and piston stopping them from that initial locking. So technically it has nothing to do with proportioning how much pressure goes front to rear but I am not 100% sure on that. Edited October 4, 2011 by Lemon Owner Quote Share this post Link to post Share on other sites
LoneWolf2U 136 Report post Posted October 4, 2011 The org poster did not say if the brake light is on or not, But a proper working dist block with shuttle centered is required. The tube has nothing to do with panic stopping or weight shift. This system is not anti lock type. It controls the pressure to the rear brakes keeping it close to same as the front. Quote Share this post Link to post Share on other sites
stangs-R-me 121 Report post Posted October 5, 2011 (edited) It [the proportioning valve] controls the pressure to the rear brakes keeping it close to same as the front. This is basically correct but let me clarify ... the "Proportioning Valve" is actually a "Pressure Reducing Valve". It "reduces braking pressure" to the rear brakes to help avoid lock up when the vehicle's weight shifts forward durring a panic stop. Also, since it is a simple FIXED valve, it does not completely eliminate the chance of lock up in slippery road conditions like ABS does. An adjustable valve is better and if adjusted far enough out could eliminate any chance of lock up ... but at the same time would be diminishing your rear braking capability in ideal road conditions. Doug Edited October 5, 2011 by stangs-R-me Quote Share this post Link to post Share on other sites
danno 128 Report post Posted October 5, 2011 These are great replies, I really appreciate this. It sounds like a rebuild kit is in order. I should also mention that the brake light is not on, and I know it works because I tested it when I replaced my hoses ( that was the first thing I did, in case they were soft). So are you saying the seals on the proporting valve or disti block? I might as well do both as long as I am in the mood to do it. Quote Share this post Link to post Share on other sites
Lemon Owner 11 Report post Posted October 5, 2011 I am more confused than ever. So what is the actual proportioning part? Is it inside the block along with the shuttle or the torpedo thing with the spring in it? Quote Share this post Link to post Share on other sites
danno 128 Report post Posted October 5, 2011 I understand it to be the torpedo thing is the proportioning part, but it works with teh distribution block somehow. Quote Share this post Link to post Share on other sites
LoneWolf2U 136 Report post Posted October 5, 2011 I am more confused than ever. So what is the actual proportioning part? Is it inside the block along with the shuttle or the torpedo thing with the spring in it? The torpedo shaped is the prop valve. The dist block has the shuttle that controls the flow of fluid to wheels. If one side fails, the shuttle moves to limit the fluid flow to the failed side and light is turned on. Quote Share this post Link to post Share on other sites
