Converting to power front discs on my 69 El Camino. Getting confused need help! The proportioning valve is the small round on that bolts to the booster and has the short line from the master cylinder to it, correct? Is the proper terminology for the brass block that bolts to the frame with all the lines the metering valve? Checking the boneyards I have found different looking metering vales that look more cylindrical than the one on my other Chevelle. I have found these on other A bodies. Are they interchangeable? They show 2 in the assembly manual. Any one know where I can buy a correct brass one ? Thanks, Scott!w

Do you need it to be correct with both parts? If no, you can go to your local GM dealer and order a brand new all-in-one combination valve. Should cost about $50.

If you do decide you need both parts, be careful you don't use a combination block with the seperate proportioning valve.

Peter

What? Thanks, but did'nt answer my question!

If it was all drum before then the block on the frame was just a distribution block with no proportioning at all. If you have a proportioning valve(metering block, combination valve I've heard all these terms) then just chuck the distribution block over your shoulder. The combination valve(meter and distribute) will do both jobs.

Jeff

My 71 Elky has the small proportioning (round one)mounted on the booster with a line coming from the front fitting of the master cylinder. one line each goes from the proportioning valve and the back fitting of the master cylinder down to the combination valve(?) on the frame,right? Anybody got a Chevelle combination valve for sale? And now the second part of the question referencing my original question, how come the combination valves on other A bodies look different? The assembly manual for 71 shows 2 different types. Are they interchangeable? Disc brake gurus please help! Thanks, Scott!

Your 71 elky setup is not original, its a setup from an earlier car. Here is how it works, 67-70 used a two piece setup for disk brakes. A "side hanger" golf ball size metering valve hung under the master plumbed to delay front brake action, and a distribution block was mounted on the frame which did nothing except send the fluid to the wheels. The metering valve had a large hex nut on the front for 67-69 and for 70 was a cast unit with no hex up front. In 71 the two pieces (metering valve and distribution block) were combined into a one piece unit (proportioning valve) that mounted on the frame in place of where the old distribution block went. Keep in mind that drum brake cars 67-72 all used the old distribution block without a metering valve as there was no braking bias needed since all 4 wheels were drum. If your car has the distribution block on the frame, most likely the car was originally all drums and someone added the metering valve off the master from an earlier car to convert to disk brake biasing. A distribution block is a solid piece of metal with flat smooth sides, a proportioning valve has bulges throughout where the internal valving is. If you want the conversion on the 69 elky to look original it will be a two piece setup with the metering valve (large nut style) under the master and a distribution block on the frame. If you dont care if it looks original you can use a 71-72 one piece unit or a replacement for the 71-2 proportioning valve mounted on the frame and no metering valve needed under the master.

Dave, thanks for the info! Can I use the porportioning valve with no nut that mounts on the booster with the the non power drum brake distribution block that mounts on the frame since the block didnt meter in the 2 piece setup?

yep, you can use the rounder 1970 metering valve with any 67-72 drum brake distribution block. FYI drum brake cars all used the same distribution block on the frame whether power or not, they just added the small metering valve to work with it for disks during 67-70.

Cool! Thanks for the info!

Very informative. I just changed to front disc brakes from drum on my 70 Chevelle and was confused as well. I put in a master cylinder and spindles from a 71 monte that had front discs. There are 2 lines that go down from the master cylinder to a "distribution block" on the frame (2 lines in...4 lines out). I have not put in a "metering" or "proportion" valve which I am assuming by everyone's input is a unit that goes on one of the lines (front brake line) somewhere between the master cylinder and the distribution block that is mounted on the frame of the car. Is this correct? Can I still use the existing distribution block that I had for the drum brakes or do I need a different one?

Thanks for your help!

If you took the proportioning valve off the frame of the 71 monte and used it then it is all you need. If not you can add a metering valve for the front brakes and keep your drum brake distribution block on the frame.

Thanks Dave but the more I read the more confused I get. (I guess I should stop reading). The original valve measures 3" X 1 1/2" and is the one off the frame when I had the drum brakes on the car. It is mounted with one bolt and bracket to the frame. The second valve I have is off a 71 Monte Carlo with front disc brakes, drum rear. It measures 6" X 2" and is mounted with two bolts. (where I don't know since it has been some time since I removed it from the Monte) From what I have seen in a few car books, the valve off the Monte is called a combination valve. Is this second valve the only valve I need or do I have to have something else with it. If I only have to use this second valve, does it mount on the frame where the first one was or does it mount up by the master cylinder. I had one 3/16" and one 1/4" line running from the master cylinder to the first valve on the drum brake system. I'm not sure whether I should change to two 1/4" lines or if I should keep it the same combo as with the original valve. Both fittings on the master cylinder are 1/4" while one fitting on the combination valve is 3/16" and the other is 1/4" so I'm not sure what size lines to use. I would love to get this brake issue done with so if anyone can give me some real detailed step by step information I would be very appreciative. I also have a pic of each valve but since I am a bit of a puter dummy I couldn't figure out how to get them on here. I can email them to anyone if need be. (rett69 at hot mail) Sorry for being such a pain in the butt people.

Use the valve off the monte, it is all you need. It is a one piece propotioning valve, also called a combination valve. Normally it is mounted on the frame on a chevelle but can be put up by the master if down by the frame is a problem (it was done this way on camaros and novas). Whatever size line was used on the monte from the master to the valve is what you want to use, not what you had on your drum system. If you also have the master from the monte this shouldnt be a problem setting up.

Thanks again Dave you've been a great help.

Here's another question,
I have a 69 velle with 4 wheel drums, BB and tall valve covers. Now I've heard that an original booster will not clear the valve cover but one from an S-10 will, can anyone confirm this? I'm going to do the front disc conversion and can get my hands on an S-10 booster,master cyl,and the proportion valve.If anyone has done this I'd LOVE to hear about it.

All I need to gather up now is a pair of disc spindles, anybody have those?