Brake distribution block question.
Thread Starter
Safety Car
Joined: Oct 2000
Posts: 4,282
Likes: 172
From: Lake Wylie, South Carolina
Brake distribution block question.
Do the Brass distribution blocks go bad? There are 3 of them I think. The main one below the master and the 2 in the back. I have thoroughly cleaned mine but it has been 5 years since they were on the car and working. Do these wera out?
Thanks
Thanks
Racer
Joined: Jan 2004
Posts: 263
Likes: 1
From: 20,000 leagues under the sea
There is a inverted flare that the flare on the line seals to. If the lines have been over tightened or to often, they can deform the brass flare and leak. I had to replace one when I redid the lines since I couldn't it to stop leaking. Hope that helps 
Thread Starter
Safety Car
Joined: Oct 2000
Posts: 4,282
Likes: 172
From: Lake Wylie, South Carolina
Thanks 68raggtop. I am thinking that what you are talking about is all I have to worry about. I don't think there is anything inside them to worry about but wasn't absolutely sure.
Thanks
BlackRat
Thanks
BlackRat
8th Gear
Joined: Nov 2005
Posts: 8
Likes: 0
I had the proportioning valve ( under the master) go bad. I went years with every vette expert telling me they don't fail. I had bad front breaks for years and tried it all many times. Finally changed the valve and fixed it. I think the valve got jamed while I was bleeding the breaks years ago.
Thread Starter
Safety Car
Joined: Oct 2000
Posts: 4,282
Likes: 172
From: Lake Wylie, South Carolina
Originally Posted by r71
I had the proportioning valve ( under the master) go bad. I went years with every vette expert telling me they don't fail. I had bad front breaks for years and tried it all many times. Finally changed the valve and fixed it. I think the valve got jamed while I was bleeding the breaks years ago.
r71,
Do you remember the symptoms you were having with the bad proportioning valve? I ordered my SS line kit and braided front lines yesterday in hopes to get brakes on the car this weekend.
Jughead,
I agree, one is a 3 way spliter with 1 inlet and 2 outlets (Driver Side) and the other is a 2 way with 1 inlet and 1 outlet. (passenger Side). I used an air hose last night and also checked the threads and inside mounting surface and they look good. Thanks
Lastly,
Has anyone replaced the front proportioning valve with an adjustable one? Is it worth it? If so which one?
Burning Brakes
Joined: Oct 2002
Posts: 914
Likes: 14
From: Aberdeen, Scotland
adjustable proportioning vlv. ..
I am convinced changing out to an adjustable Proportioning vlv is the way to go. My car seems to have a funny bias, why i don't know. Its real twitchy in the wet, maybe to much bias at the back, but that's a guess to me. I wonder if my stock, old vlv is just stuck or worn?
I am not REALLY sure how the stock vlv works, is it front to back or side to side bias? I thought it was side to side for some reason, but can't recall, i.e. if you loose a brake line on the right you can still stop with the left? Help....
carbster
I am not REALLY sure how the stock vlv works, is it front to back or side to side bias? I thought it was side to side for some reason, but can't recall, i.e. if you loose a brake line on the right you can still stop with the left? Help....
carbster
Race Director
Joined: Nov 2000
Posts: 11,872
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From: Waterloo ontario Canada
Originally Posted by carbster09
I am convinced changing out to an adjustable Proportioning vlv is the way to go. My car seems to have a funny bias, why i don't know. Its real twitchy in the wet, maybe to much bias at the back, but that's a guess to me. I wonder if my stock, old vlv is just stuck or worn?
I am not REALLY sure how the stock vlv works, is it front to back or side to side bias? I thought it was side to side for some reason, but can't recall, i.e. if you loose a brake line on the right you can still stop with the left? Help....
carbster
I am not REALLY sure how the stock vlv works, is it front to back or side to side bias? I thought it was side to side for some reason, but can't recall, i.e. if you loose a brake line on the right you can still stop with the left? Help....
carbster
Get rid of it. Plumb the front of the master to the front brakes and the back to the back and keep both systems seperated.
You do not need a proportioning valve. That is already done in the calipers. Front is 1 7/8th and the back is 1 3/8th. That is all the proportioning you need.
The factory didn't have one so why add it???
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Race Director
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Norval,
You keep saying it's not a proportional valve, why? Or do you have proportional valve and metering valve (used in disc drum applications to overcome the fact that drum brake linings need some travel before they grasp) mixed up???
The front-rear brake size bias is indeed a form of proportioning but the proportioning valve increasingly restricts flow to the rear brakes the harder you brake
You keep saying it's not a proportional valve, why? Or do you have proportional valve and metering valve (used in disc drum applications to overcome the fact that drum brake linings need some travel before they grasp) mixed up???
The front-rear brake size bias is indeed a form of proportioning but the proportioning valve increasingly restricts flow to the rear brakes the harder you brake
Last edited by Twin_Turbo; Jan 10, 2006 at 02:31 PM.
Race Director
Joined: Nov 2000
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From: Waterloo ontario Canada
Originally Posted by Twin_Turbo
Norval,
You keep saying it's not a proportional valve, why? Or do you have proportional valve and metering valve (used in disc drum applications to overcome the fact that drum brake linings need some travel before they grasp) mixed up???
The front-rear brake size bias is indeed a form of proportioning but the proportioning valve increasingly restricts flow to the rear brakes the harder you brake
You keep saying it's not a proportional valve, why? Or do you have proportional valve and metering valve (used in disc drum applications to overcome the fact that drum brake linings need some travel before they grasp) mixed up???
The front-rear brake size bias is indeed a form of proportioning but the proportioning valve increasingly restricts flow to the rear brakes the harder you brake
In my old age I assume too much. Sorry
Race Director
Joined: Sep 1999
Posts: 11,361
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From: Plano TX
I read an article from the arly 70's with Duntov where he stated the 71 Corvettes did not use a proportioning valve. The magazine writer was speculatng that's why he liked the BB brakes better as the brake balance was off a little with the lighter SB.
Race Director
Joined: Dec 1999
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well..now I'm not sure anymore LOL why apologize Norval? You may just be right..and I may be wrong judging by what zwede says, you know..I have one lying around, I'll take it apart and see if there's just a plunger in there to trigger the switch or also a prop valve. Will let you guys know, for all we know GM just used a prop valve block and just machined it for the punger/switch and nothing else...wouldn't be the 1st GM surpise 
Melting Slicks
Joined: Nov 2001
Posts: 2,668
Likes: 43
From: Eastern US XX
Originally Posted by Twin_Turbo
Norval,
You keep saying it's not a proportional valve, why? Or do you have proportional valve and metering valve (used in disc drum applications to overcome the fact that drum brake linings need some travel before they grasp) mixed up???
The front-rear brake size bias is indeed a form of proportioning but the proportioning valve increasingly restricts flow to the rear brakes the harder you brake
You keep saying it's not a proportional valve, why? Or do you have proportional valve and metering valve (used in disc drum applications to overcome the fact that drum brake linings need some travel before they grasp) mixed up???
The front-rear brake size bias is indeed a form of proportioning but the proportioning valve increasingly restricts flow to the rear brakes the harder you brake
Former Vendor
Joined: Nov 2005
Posts: 683
Likes: 1
From: Mounds View Minnesota
I'm sure that there was no Proportioning valve on my '69.
I'm also sure that the rear brakes locked up before the front <--Bad.
(you want the front to lock up just before the rears, otherwise you will spin the car when the rears lockup, esp in a corner.)
I'm pretty sure later vettes did have a proportioning valve built into the distribution block.
The brass thing all the brake lines run though is just a switch that lights up an idiot light. Without it grandma wouldn't know anything was wrong...I also believe the fact that the pedal goes to the floor on failure and has to be pumped up is by design, they don't want people driving cars with bad brakes.
I would recommend an adjustable rear proportioning valve in all vettes, otherwise I don't believe it can be balanced properly.
The switch / distribution block does nothin unless there is a failure, whereupon it makes the failure quite obvious, so there is really no reason to remove it.
I'm also sure that the rear brakes locked up before the front <--Bad.
(you want the front to lock up just before the rears, otherwise you will spin the car when the rears lockup, esp in a corner.)
I'm pretty sure later vettes did have a proportioning valve built into the distribution block.
The brass thing all the brake lines run though is just a switch that lights up an idiot light. Without it grandma wouldn't know anything was wrong...I also believe the fact that the pedal goes to the floor on failure and has to be pumped up is by design, they don't want people driving cars with bad brakes.
I would recommend an adjustable rear proportioning valve in all vettes, otherwise I don't believe it can be balanced properly.
The switch / distribution block does nothin unless there is a failure, whereupon it makes the failure quite obvious, so there is really no reason to remove it.
Last edited by Corvette Engineering; Jan 10, 2006 at 03:12 PM.
Race Director
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thinking about it, not having a prop valve would make the BBC brake worse, sie the braking force at the rear is not reduced the heavier weight up front would cause the rear wheels to lock even sooner.
pws69, yes but the differntial valve/brake light switch is always there, as a bare minimum. Apart from the differential valve the block can hold a prop valve or a prop valve and a metering valve, the dif, prop & metering valve combo is used on disc/drum applications and the differential/prop valve on disc/disc applications however Norval says the vette only has the differential valve and I'm not 100% sure, I'll take mine apart to be certain.
pws69, yes but the differntial valve/brake light switch is always there, as a bare minimum. Apart from the differential valve the block can hold a prop valve or a prop valve and a metering valve, the dif, prop & metering valve combo is used on disc/drum applications and the differential/prop valve on disc/disc applications however Norval says the vette only has the differential valve and I'm not 100% sure, I'll take mine apart to be certain.
Last edited by Twin_Turbo; Jan 10, 2006 at 03:21 PM.
Le Mans Master
Joined: Jun 2003
Posts: 5,135
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From: Umeå Sweden
Norval how did you do when you removed the valve did you get new lines from the master to the wheels or did you reuse the old ones?
if so what do you have insted of the valve?
mine is leaking in the back so i thought i would remove it and se how it feels
if so what do you have insted of the valve?
mine is leaking in the back so i thought i would remove it and se how it feels
Senior Member since 1492
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From: Just because I'm paranoid doesn't mean people aren't out to get me...
St. Jude Donor '09
I remember reading here on the forum (waaaay back) that the proportioning block ended in '68 and from '69 on it's just a distribution block. 
Drifting
Joined: Oct 2003
Posts: 1,426
Likes: 1
From: VetteMOD
St. Jude Donor '05-'07
Originally Posted by Jughead
I remember reading here on the forum (waaaay back) that the proportioning block ended in '68 and from '69 on it's just a distribution block.
As far a leaking (original topic). At the very minimum, when replacing lines, I would replace the block at the driver side rear wheel. If it leaks with the lines in place it is a b*tch to replace but EZ when replacing lines.
Last edited by BBShark; Jan 10, 2006 at 08:40 PM.