Another prop valve question

[JoeGrapes]

Years ago I used the brake system from a '74 front disc car. Last year I changed all the brakes to Wilwood disc brakes. I put a valve in the rear line but kept the stock front disc/ rear drum master and prop valve. I just got a Mopar plastic master cylinder from Dr Diff. They said if I want to keep my stock iron prop valve i need remove the guts. When I asked what exactly I need to remove they said just remove the guts. Am I suppose to remove all the valves so it becomes a distribution block?

[dodj]

No. I have sounds like the same setup in that i have front disc/rear drum prop valve with a wildwood restrictor valve in the rear line. Also the newer plastic m/c.You still need to proportion between the front and rear. 

[johannes]

A drum rear brake master cylinder has "non return valve rubber thing" on the master cylinder outlet ( in front chamber)... Remove rear  brake pipe fitting...use a needle to puncture rubber thingy now accessible on master cylinder.... This to preventrear brake "hanging on when not in use".... As for tuning the rear brakes....find a " gravel  road" ...and  see from the skid marks if tuning is OK...... Just my way of seeing  solution... 

[Bullitt-]

Several here are using the Wilwood adjustable valve

http://www.cuda-challenger.com/cc/index.php?topic=109710.msg1081022#msg1081022

http://www.cuda-challenger.com/cc/index.php?topic=66387.msg695264#msg695264

http://www.summitracing.com/parts/WIL-260-11179/

[JoeGrapes]

dodj, you left the original front disc rear drum prop valve in place with out making any changes to it? You car stops fine? Did you find that you had to adjust the rear brake line valve much?

[burdar]

You don't need a prop valve with 4 wheel disc brakes.  All you need is a distribution block.  You can use a 4 wheel drum distribution block.  I don't think gutting the stock prop valve is a good idea.  It would become a distribution block at that point but, you would also be doing away with the safety feature of blocking off one side of the system if you had a leak. (The front and rear sides of the system would be open to each other.  If you have a leak at the back, you would lose all of your braking since both sides are connected to each other.)

[dodj]

dodj, you left the original front disc rear drum prop valve in place with out making any changes to it? You car stops fine? Did you find that you had to adjust the rear brake line valve much?

It stops much better with the rear line restricted with the valve. My rears would lock up much sooner than the fronts which was, lets say, less than ideal. I set it up a few years ago and remember thinking I had to restrict it more than I thought I would have to. I just went and found some lightly used road and did repeated hard stops and adjusting until the brakes behaved the way I liked 'em.

I just reread your original post. My brakes are drum in the back. So not the same.

[JoeGrapes]

bursar, I looked at the cutaway of my prop valve and removing the spring that limits the pressure to the rear brakes should not have any effect on the safety operation of the valve. The two systems look to be separated by a plunger with O rings that operate the brake warning light if one side should loose fluid. Taking that spring out should not effect that. But, I'll find out one way or the other when I get the car back on the road. I'm using a Dr Diff master and I had already installed I valve in the rear brake line if I need adjustment.