Ive been posting about converting front drums to discs on my 68 chevelle. I have everything i was told i needed (all the brakes, spindles, new MC WITH new booster) BUT i didnt get a proportioning valve (metering valve? are they the same thing/function?) The reason i havent gotten that is because on my donor car (69 ss with the disc brakes) there is something connected to it's master cylinder. Im thinking this is the 'valve' i need... it is connected to the front outlet on the MC by 5 inches of brake line, then there is an outlet on the 'valve'.

So, does anyone know if this is what i need? It sure would be nice..

Bubba my 1968 SS chevelle (http://www.garsworld.com/chev/default.htm) graemlins/waving.gif

I wish someone would answer your post. I need this info too.

I just found this info. It might help. http://www.mpbrakes.com/valving.htm

There are 2 valves on the 69 disc brake setup. YOu do need that proportioning valve that is under the master cyliner. It delays the fluid to the front so that the front does not nose dive. There are a total of 2 valves on the 69 setup. The one I described above, and the one on the frame. The one on the frame is nothing more than a distribution block.

So that valve that i was inquiring about (that is hooked to my MC on my donor car) is the proportioning valve that i need? I have the square-looking block on my frame already... So i guess i am set right? One more thing, do i hook that prop. valve to the front brake or the back brake line outlet (from the MC)?

Thanks for the help AND the link 68wagon

That's the one you need. It goes in line with the front line of the master cylinder. You can get new lines from The Right Stuff pre bent in either stainless steel or OEM material. Just call up and say you need a set of front lines for a 69 with power disc brakes graemlins/thumbsup.gif

I just bought a 69 elco with drum brakes. The old owner added a power booster and now the car nose dives. The brake light also comes on. I an going to replace the master cylinder today. Is the proportioning valve for disc the same as for drum?

BlueSS is right the block under the master is the one you need. Bill68 the valve is different from disc to drum. Disc needs more pressure than
drum. It also needs residual pressure to the front discs that the valve provides. I bought a kit from www.classicperform.com (http://www.classicperform.com) they gave me a valve that mounts to the frame. This is where the distribution block was.
My two cents
Rob

Um...isn't the 1969 setup the same as the 70?

If so there is another valve on the frame near the rear axle. I forget what is does but you need it too I believe...I didn't have it and I had a brake light come on instead of the brakes and ended up in a ditch. 5mpg faster and the frame would be scrap

Double check on this is my advice or order a 71 style valve that combines the valves into 1 that mounts under the MC

Also I don't think there is a valve for drum cars, drums require equal pressure, discs require 70/30 front the rear distribution if I am correct

Disc take more to work, so if its nose diving with drums all around, maybe it doesnt need the valve on front?

These valve systems were too complicated before 71, that's why they went to a single block version for 71. I have a super chevy that went through the details of this is said 69 and 70 disk cars had 3 valves (2 proportioning valves and the distribution block between the front sides) and the 71 has only the one large valve

The 69 setup has the same valve as a 70 up front. That block in the rear is ONLY ON 70's. I don;t really think it does anything, it's just kind of there, you don't really need it.
Here is how the 69 system works:
There is a proportioning valve under the master cylinder which delays the fluid to the front. There is a distribution block on the side of the frame which sends fluid to all 4 corners, that is all that block does.
Now a 1970 system:
same as 1969 but has that extra block on the rear part of the frame. I ran my 70 for a few years without it, never had a problem. I only put it on there recently since I got a 1970 El Camino with discs from a junk yard so I got a whole new line kit and ran the correct setup for 1970.
Drum systems: Only have 1 distribution block on the side of the frame. A drum brake car will nose dive if you slam on the brakes hard enough, I've been in a few situations with my 69 manual drum car where I have had to do that.

You have to bleed the 69 and 70 disc systems in a different manner than the rest. There is a little button on the back of the prop valve that needs to be depressed while bleeding the fronts.

The best and easiest thing to do is take ALL the brake parts off the donor car and transplant them to your car.

Originally posted by robseg:
Bill68 the valve is different from disc to drum. Disc needs more pressure than
drum. It also needs residual pressure to the front discs that the valve provides.
Rob You might want to double check this, if you are using more than 2psi as a residual check valve you are dragging the front brakes. The rears drums usually use about 10psi to prevent the wheel cylinders from fully relaxing resulting in a low pedal. Disc brakes are designed to have the piston retract a very small amount to prevent heat build-up and premature wear of the front brakes.

If you really want to tune your own brakes, run NO prop valve and make sure the 10psi valve is still in the master, then run an adjustable rear block off and tune it till the rears won't lock until the fronts do. Best way is to start with too much pressure to the rears and then back off slowly.