I'll be doing a disc brake swap on my 70 convertable. I am trying to find that little block that bolts to the rear chassis behind the rear drivers side back seat.

Where can I get one I see them on e-bay but it's impossible to get one.

Does anyone have a substitute or is there something else I can use.

I note from a friend there are other cars whom had them but with different pressure ratings - would 70 CAMARO work? as I have access to this part see pics - if I remove the little block from the proportioning valve can I use it?


http://my70ss.homestead.com/files/CAMARO_VALAVE.jpg

http://my70ss.homestead.com/files/CAMARO_VALAVE_2.jpg

Any help here would be great - thks

Rich

hey Rich
Not sure if you can get them new or not... I haven't been able to locate any so far. Might want to check with Sundell's and see if they can get you one off of one of their parts cars. And as far as I know that block on the rear suspension is just a junction block but I could be wrong.

Fig,

Thks - do you have a contact for Sundell? I'll give them a shot - I do know the valve has a purpose for the back brakes as the front disc require less pedal pressure - so this valve evens the pedal pressure to the rear brakes and I beleive keep them from locking up - I think that is how it works.

Anyone else with ideas?

Thks

Rich

I dont know what the block on the rear is, but I know I have never installed one and didnt have a problem. I have put 1970 setups on other cars and just used the factory metering valve under the master (part on the left in your pic) and the factory distribution block on the frame. The metering valve delays the rear brakes so they dont lock up, is the extra piece you need a residual pressure valve? Either way I have had no issues not including it.

Rich
I will have to look up the number to Sundell's when I get home tonite, unless someone here beats me to it... Leo? Tom R?

Also from what I have seen the block that is not in the picture you have is simply a junction block. I still have yet to find a reason why they put in a 2 piece line. If ya find one let me know cause I will need one for my 70 once I buy the lines later this year.

rich the part your looking for is just a tee fitting ground up part # fblk-1 should work check it out

Robert,

Thks - however that part will not do. After more research I have learned the little block is called a hold off valve or rear brake pressure regulator valve, it had a function of regulating or keeping some presssure on the rear brakes. In 71 they did away with it as they improved the proportioning unit bolted to the chassis under the booster.

I had also learned there are two productions of this block a 250lb valve 1rst design 3980770 (stamped N). And a 400lb valve 2nd design 3987805(stamped S) which is what is in my 70 SS. The 1970 Camaro valve I show above may be part number 3980978 - I am hoping it's just a different number due to the mounting.

If anyone else has any other knowledge on this part either to confirm my findings or add pls chime in.

I am sure many people have swapped to discs on a 70 and never used the block, it's possible that it's function was minimal in which may not be needed, however before I go that route I would like to be sure.

Thks

Rich

I believe what you are looking for is a residual pressure valve. From what I know if you have a front disc/rear drum configuration, you need a 10 psi residual pressure valve for the rear drums and a 2 psi front residual pressure valve plus a metering valve for the front discs.
I'm currently doing a front disc conversion on my 70 and that is what they told me I need for the setup. I'm trying to figure out what valves my 70 drum/drum configuration came with stock, so I know what to get in addition to the kit (see my post in this section).

I believe if you use a 71+ Master/Distribution block, the "acorn shaped" valve is built in.

But in answer to your question, I think the valve is specific to 69-70 model years.

Rich,

I'm no expert on this subject, but i've owned a few 70's with disc brakes, and the valve on all of them wasn't in the back, it's mounted on the drivers side frame under the steering column. Here is a picture of the valve used on my 70 convertible.

http://members.cox.net/chevelle/brake.jpg

I may have mis-understood your post, but I don't want you looking for the wrong part. I don't know where to get a new one either, but i'll be glad to take pics or post part #'s from the (2) 70's I have right now. Hope this helps.

Jim

chevyjim,
all the info is in the archives, but basically for 70 the brake system was in separate pieces..metering valve under the master to delay rear brake action, distribution block on the frame (same as drum cars), and apparently a pressure residual valve in the rear line. I know pressure residual valves are available aftermarket because a friend uses them when setting up street rod frames with the master cylinder under the floor. I myself have never used one, so far when converting cars to disks with the 69-70 setups I have used I have not had a problem, I only used the metering valve and distribution block. Another thing, is the pressure residual valve unique to 1970, If it is, then possibly it is built into the master cylinder for 1967-69 and by using the earlier master you would not need the valve.

Dave,

Sorry, but I didn't see the earlier post you made addressing the valve that I was talking about. I'm going to look at my cars and see if I can find the valve mounted in the rear. I didn't know it existed. Sorry for the confusion.

Jim