Proportioning valve problem

[mjoc1]

I have a 1967 Buick GS400 convertible. It came to me with drums all around. I just did a disc brake upgrade to the front. I used the 12 inch rotors. I have installed a new master cylinder and power booster. I have plumbed in a proportioning valve to the rear brakes.

Now My problem is that I still have the original proportioning valve installed at the frame behind the cross member. What I need to know is how can I delete this without re plumbing the whole system. Is their a way to install somekind of tee to the front and a 90 the rear?

Is a distribution block the same as a proportioning valve if not can I just install one of these?

The brakes are working now but I know they should be working alot better. I can't get them to lock at all. And at slow speed they don't seem to work well at all.




Mike

[Apogee]

If I'm not mistaken, the item mounted to the left frame rail on a drum/drum car is just a distribution block...no proportioning valve needed with the drum/drum setups. It may have a shuttle valve between the front and rear circuits for the brake balance switch, but that's it usually. It could be rusted up inside...always a pretty good assumption on cars of this vintage.

What disc brakes are you running up front? Since 12" rotors were not an option on the 67 GS400, I'm assuing it's aftermarket. Did you do a B-body (GMTS) spindle swap or something? What bore size master cylinder are you running? What booster? How much vacuum does your engine make at idle.

Sorry for the all of the questions, it's just easier to get the obvious stuff out of the way up front so that we can try to see the bigger picture.

Tobin
KORE3

[mjoc1]

Yes I did do a spindle and brake upgrade. The kit came from Hotchkis a few years ago. It came with a booster I believe it is called the 9 inch diaphragm I believe it is 1 1/8 in bore. The master cylinder is a 70 Impala disc/ drum unit. I have an adjustable proportioning valve in the rear line I don't know how much vacuum it makes at idle what should it make?

Does the distribution block work? Or do I need to go a different route?
If the distribution block works can I order a new one from you?


Mike

[MonzaRacer]

All you need is an adjustable unit from any of the speed/brake emporiums, Tobin can recommend which he likes. With your setup a inverted flare T for the front lines is all you need then the rear section straight to the rear brakes.

[JRouche]

Basically what you need is two lines coming from the master cylinder. One heads to the front, branches off to two lines, one for each side, simple T fitting, I branched mine at the center of the car.

Then for the rear it come off as one line to the proportioning valve, Im assuming its an adjustable valve right. Come off that valve and Tee it again (simple block) for each side of the rear wheels. Its a simple system.

Remove all the original blocks, they are just a problem and really not needed. Keep the brakes simple. It really is a simple plumbing job. JR

[NOGO]

With a disc/drum setup you should be running a combination valve. The combo valve includes a metering valve and a prop valve in one. The metering valve momentarily sends pressure to the rear brakes before the fronts to take up slack between the shoes and drums. The prop valve limits the pressure going to the rear brakes because of load distribution during braking. Without this valve the front brakes are going to wear faster and possibly overheat during spirited driving.

[JRouche]

With a disc/drum setup you should be running a combination valve. The combo valve includes a metering valve and a prop valve in one. The metering valve momentarily sends pressure to the rear brakes before the fronts to take up slack between the shoes and drums. The prop valve limits the pressure going to the rear brakes because of load distribution during braking. Without this valve the front brakes are going to wear faster and possibly overheat during spirited driving.

Good point. For some reason I was thinking he had discs on the rear also. Guess Ive been staring at my car too long JR