Proportioning valves,metering valves, combination valves, all very confusing. My question is, if I convert my 69 El Camino to power discs in front and discs in back, why can't I use a master cylinder from a 65 to 79 Corvette master cylinder with none of the above mentioned valves? The corvettes were 4 wheel disc brakes and did'nt use any of the valves.(except J52 option on the early L88's) Thanks, Scott! graemlins/beers.gif

who says you cant? Still would want a distribution block if you want a brake warning light.

Man, Dave you're always there when I need you!So a 69 Corvette 4 wheel power disc brake running through a distribution block will work when converting to 4 wheel disc brakes on my Elky with out metering or proportioning valves! Totally cool! Thanks again, Dave!

I beleive all brake systems need some type of prop. valve otherwise the brakes would lock up. I dont think you can use just a dist. block, you need a disc/disc prop. valve. You can get one off any GM car that had 4 way disc brakes.

Or better yet, get an adjustable prop. valve like Wilwood's. Since 69 El Caminos never came with 4 wheel disc brakes, any prop. valve you borrow from another vehicle won't optimized for your Camino. May as well get an adjustable and dial in your brake balance.

Boy did I screw up! Upon further investigation I found that the Vettes came with a proportioning valve bolted to the frame! If the Vettes and the El Camino weighed about the same, wouldn't the disc/disc proportioning valve work O.K.? :rolleyes:

I dont believe the prop valves really vary from car to car. If you go to the local chevy dealer, its the same part # for anything in the 80's vintage. My disc/drum prop valve is off a monte I think. Its the same part # for a chevy truck, caprice, ect... Also, companys like MP Brakes sell one style prop valve for either disc/disc or disc/drum. I dont think what the actually vehicle its going on matters.

I'm a little late but I'd think you would need one. Without some type of valve I bet you will get rear lock-up under heavy braking and that is a very bad thing (the rear wheels try to pass you and sometimes they are successful).

Peter

Why would the rear brakes lock up first if all 4 corners are disk? With the disk/drum setup its obvious that the front disks need a delay because of the different braking setups, but with all 4 corners why would there be a delay needed somewhere? Would it be that different than 4 wheel drum setups that use no braking bias? I wonder what the 4 wheel disk 80s T/As used, maybe that valve would be still available.

Two words...weight transfer! More loading on the front brakes than the rear when braking.

but then shouldnt a 4 wheel drum system also have the same problem? There is no braking bias with a 4 wheel drum system.

They do. Most panic stops in 4 drum brake cars get rear wheel lock up before front wheel lock up. As was mentioned earlier it has a lot to do with weight transfer. The front dives and unloads the rear. With less weight on the rear and the same braking pressure the rear wheels will lock up first.

Update on my disc brake conversion....Now that with everyone's help I only had to use the proportioning valve I already had, it was time to put it all together...and guess what? I figured since I had it all apart I would change the front brake lines as well as the two lines from the master cylinder to the prop valve. Now I am having trouble getting brake lines since the ones in the stores I have looked at have fittings that don't match up with what I am looking for. What I need and measured is: front brake 3/16" line from m/c to prop has a 1/2" threaded fitting on each end while rear brake m/c to prop has 1/4" line with 7/16" threaded fitting in prop valve and 9/16" threaded fitting in m/c. I can just buy the lines but I can't find anyone with the fittings. I tried UAP, Northwest Auto, GM, Canadian Tire, etc. in Canada and no one has been able to help. Any ideas? Is this setup the way it is supposed to be? I would have thought the front brake line would be the larger one. I got the m/c and valve from a 71 Monte. Does anyone know of a publication that would show this newbie how the setup is exactly?

Thanks Stephen

The line sizes, 3/16" and 1/4", are standard but chevy used different size special nuts to keep the wrong parts from getting put on the wrong car. If you want to replace the lines you will have to cut your nuts off (OUCH!) and use them with new lines. A double flare kit makes brake line fabrication easy. The only place I got the different sized nuts new so far was from JC Whitney of all places. I bought a brake line kit which came with a roll of brake line and an assortment of nuts. There are adapters to make things fit but they make the brake system look cobbled together IMO.