Yeah im converting my 72 chevelle from drum to disc. Ive pullled the drums off and replaced the ball joints and put the disc on. Im ready to put the booster on now. The Question I have is the porportioning valve that is used with the drum brakes can it be used with the disc's or do I have to switch that too. The drum valve is attached to the frame with a lil bracket and one bolt. The valve that I pulled with the disc setup has 2 bolt holes that attach it to the frame, and the brake lines look a lil different. I was told that I would have to switch the valves. If any body out there that has done this and had experience with it Knows any info or can let me in on something would be great. It would be nice to use the drum valve cuz it would save me a lil work. but if someone has done this and knows the valves (the one for disc that is attached to frame with 2 bolts) im talking about. Did you have to drill the 2 holes and tap them for these bolts to thread in or what. Please let me know something. Thanx Brian

Hey Brian,
I am very sure that you cannot reuse the proportioning valve from the drum setup. I am switching from drums to discs on my 65 and had to buy a new one. The spindals and discs you picked up, if they came off of a donor car, get the valve from there.
If you cannot, there are companies that make these.

Valve from Ground Up (http://www.ss396.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=396&Product_Code=FM-1350&Category_Code=BRA-001)

Mine came with the master cylinder and booster as a kit.
These are pricey, but look at what you are protecting.
John C.

The valve cannot be reused. For me the reason the lines were different from drum to disc was i had a single Master cylinder vs. a dual. There was an added line that had to be run to the proportioning valve. I bought one from henshaw's (didn't grab the one off the donor car) and mine bolted to the same location on the frame.

Good luck.

stompn, that valve that you see bolted to the frame rail is not a combination or proportioning valve. It is merely a distribution block with a warning lite switch in the middle. For disc brakes, you need a combination valve like the one you describe with holes for 2 bolts. I just converted my 69 from drum to disc on front. There is not enough room with the engine in the car to drill a hole and tap it for both bolts unless you have an angle drill. What I did was made a braket out of flat iron on which I bolted the combo valve, with the front protruding a bit, and used the existing bolt hole that once held the distribution block. Although this setup only uses one bolt holding the valve to the frame, once you attach all 5 steel brake lines, it is solid as a rock. Be careful when you mount the combo valve on the frame rail to not interfere with any shifter or clutch mechanisms. One alternative, mount that combo valve on a braket under the master cylinder. Lots of GMs did this and any salvage yard with mid 70 GM's should have brakets. Then you can leave the distribution block on the frame rail and simply plumb new lines to it. In my case, I didn't want any more clutter under my hood with home bent brake lines.

thanx for all the info. and some good ideas. I know what valve your talking about bhawk it hooks to the master cylinder. and has a line running from master to valve and then to dist. block. I got the disc setup off a 72 monte and she didnt have the master or booster but she had a porportioning valve like I have on mine. Im thinking that she had that valve becuz we just put a disc setup on my buddies elcamino and it came off a monte which had that valve. Im gonna look around for that valve that bolts to the master. I bolted the spindles on tonight and thats gonna be my next move. Thanx for all the info everyone.
Brian

stompn, I actually wasn't referring to the round bullet shaped valve that bolts to a bracket on the master cylinder. That valve is often called a "metering valve" and was used around 68 to 71 only. It however does a job similar to the post 71 combination valve. If you find a metering valve try it. But they are rare used, and are expensive at restoration parts suppliers. I was speaking about the mid 70's GM cars, like a 74 Nova, that has a braket bolted the the master cyl. that holds the combination valve that came with 71 and later cars. Go to www.mpbrakes.com (http://www.mpbrakes.com) for more info on these valves. They explain better than I can.

nice site, so if I use this valve that your talking about can I still use the same distribution block on the frame and just hook the same lines into this valve or do I have to run new lines from the new valve down to the distribution block on the frame.( METRIC OR SAE )?

If you go with a bullet "metering" valve you can leave the distibution block on the frame rail and hook the existing line to the metering valve and run a short one from the master to the meter valve. However, be mindful that if you have a master cylinder that does not have the residual valve built into the rear outlet like they had in 1968-70 or so, you won't have that 10 pounds of residual pressure always in the rear brake lines that help to get the rear shoes moving quick to help stop the car. The MP brake site speaks about the residual valve and how it is built into the combo valve. It is my understanding that after 1971 the master cylinders no longer had the residual valves built into the rear outlets because GM went to a combination valve on the frame rail that did both functions, metering (or slightly delaying) fluid to front disc brakes and residual pressure retention in the rear line. To do this job right, I would recommend mounting the post 71 combination valve where it is easiest for you, and face the difficulty of plumbing it with correct fittings. But once done, you have the proper functions in one valve. I can email photos of a braket off a 74 Nova that I got at a bone yard and haven't used. It mounts the combo valve to the master.

can I use the one that johnyac was talking about. check that link out that he sent from ground up. the one im talking about is this one from ground up. go to ground up website and search this number fpv-89... and email me a pic of that bracket you were talking about. Thanx

If it matters, the valve that I have........ MP Brakes Combo (http://www.mpbrakes.com/mp22.htm)
It looks just like the unit that ground up offers (same price too). Each has a mounting bracket.

Got luckey and scored a new MP Brakes Booster,master Cylinder, and combo valve (with brackets and lines) off of Ebay for far less than buying it from MP.

If you have the time, Ebay may be the way to go.
As far as running new lines to the distro block, I am just going to redo all of mine from scatch. A 39 year old system may have seen better days. Had an 89 Lebaron actually blow a hard line once, not going to take that chance on my Chevelle.

I am at a loss as far as telling about bullet metering valve and residual pressure. New lessons for me, thanks Bhawk.
John C.

Stompn, the ground up fpv-89 is a repo of the original metering valve used circa 67-69. Johny? has provided 2 links, one to ground up and one to MP brakes. Both of those depict the combination valve I am speaking about, and which I would recommend. From reading posts on this forum I believe GM sells that same combination valve without braket or short lines for about 50 bucks. Search combination valve, proportioning valve, etc to get the part number. But it is not easy to bend and flare new short lines so maybe 149 bucks isn't unfair since it gives the braket and short lines. I will email photos of 2 brakets I have somewhere in my shop at home, hopefully this evening.

Hey Bhawk,
Question about bending a flaring brake lines.
I do HVAC work and thought that using the same tools I use for bending and flaring copper lines should work on the steel brake lines. Are there different tools specialized for steel lines?

John C.

ya'll helped me out big time and I appreciate it. Im going up the road this weekend to a nice classic junk yard that has a few cars in it and im going to try and go that way. But if I cant find what im looking for I think Im going to buy that combination valve that johnyac showed me. Im just curious if I buy that valve can I still use the distribution block that I have on frame now. And also I would still like to see that pic so ill know what to look for. Thanx alot..... stompn Ill keep yall posted

What if I intend to use the existing power booster on my orig disc/drum 70 for a 4 disc setup? How does the integrated valve on the master cylinder work with this ? Can I still use my distribution block I have mounted to the frame or do I ditch it? I'm confused...I have all the brakes, I just want to make sure I'm ordering all the right hardware for the lines....the frame is currently POR15-ed and seperated from the body so I can go any way with the 4disc system....which is best????

Hey Zefhix,
Not the pro on this but while reading through the July issue of Chevy Performance, pg 66, they kind of touch on an answer.
It goes (from MP Brakes) that to do a disc/disc setup requires a matching disc/disc master cylinder and changing to a four wheel disc proportioning valve. The difference between the drum and disc setups are the hydralic pressures needed to operate the drum vers disc. Drums need 400-500psi and discs need 800-900 psi.
That was a supprise to me!
I would not think that you would need to change the booster.

Anyone else seen or know if this is correct?

As for the distro block, perhapse a question for MP Brakes.
Funny thing is this articles about installing bigger drums on the rear.
John C.

johnyac, I'm not sure if your tools will work. Brake lines require what is called a double flaring tool. It is made in two steps. First you make the flare then you install a second "die" and fold the lip of the bell you made onto itself. It is not easy, but takes practise to do this well. Search double flare or the like in this forum and get lots of discussion on how to make a good double flare. If you are buying a tool, you must pay more and get a good one. lots of cheap junk out there. Stompn, I will email pics later today of a braket and combo valve. I agree that 4 wheel disc setups do not use the same combination valve as disc drum cars, and a different master cylinder also.

Knew about the cobination valve from MP's website but didn't know I need a different master cylinder.....good info. Thanks. I guess I should ditch the distribution block..... smile.gif