proportioning valve
Thread Starter
Instructor
Joined: Feb 2004
Posts: 210
Likes: 0
From: woodstock ga
proportioning valve
ive read other forums but i am still confused...
Can the brake proportioning valve or low pressure switch( whatever its called) be removed from my 75 saftly? Will it cause better or worse braking? Has anybody done this?
Can the brake proportioning valve or low pressure switch( whatever its called) be removed from my 75 saftly? Will it cause better or worse braking? Has anybody done this?
Pro
Joined: Mar 2005
Posts: 683
Likes: 4
If it's working, leave it alone. This valve enables two wheels to have braking ability in the case of failure. Such as if you loose front brakes, then you still have rear brakes. This valve will turn on the brake light on the dash.
Le Mans Master
Joined: Jan 2000
Posts: 8,918
Likes: 27
From: New Hill NC
This is not a real proportioning valve. It is only a switch that indicates if the pressure is unbalanced between the two systems. I dont know why you would want to remove it, but it would make no difference.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Originally Posted by Steve COSD
If it's working, leave it alone. This valve enables two wheels to have braking ability in the case of failure. Such as if you loose front brakes, then you still have rear brakes. This valve will turn on the brake light on the dash.
I have advocated getting rid of this light switch years ago. I removed mine and found an improvement in rear brake performance.
With this light switch removed if you loose one end of your brakes the other end still sees full pressure, not a reduced pressure.
When bleeding the system with this switch out you will immediatley notice the peddle feels firm even before completley the other end.
The only down side to this is the brake pedal feel will feel normal when in fact one end is bad.
I did this to my vet and 2 mustangs and everyone notice an improvement over running the valve.
Get rid of it.
Other them myself has anyone else here really done it, can comment first hand on what it does getting rid of it??????
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Originally Posted by wombvette
This is not a real proportioning valve. It is only a switch that indicates if the pressure is unbalanced between the two systems. I dont know why you would want to remove it, but it would make no difference.
While holding the brakes on have someone open a bleeder, any bleeder and see if your foot suddenly falls to the floor then tell me it doesn't make a difference.
I know that with the switch out the peddle will continue to feel firm. One end will still get full braking effort.
Le Mans Master
Joined: Mar 2001
Posts: 6,638
Likes: 287
From: Ann Arbor Michigan
See the post listed below. 75' through 82 DID have a proportioning valve, 68-74 did not.
http://forums.corvetteforum.com/show...post1550741836
http://forums.corvetteforum.com/show...post1550741836
Race Director
Joined: Oct 2000
Posts: 14,865
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From: central FL, near the beach.
norval
i bypassed the valve/switch on my 67 galaxie.
Years ago, 1990, i had a rear leak and lost ALL brakes
even pumping gave nothing.
NOW it has adequate brakes w/1 open bleeder.
the pedal is lower, but firm, and can lock the wheels.
see current topic
http://forums.corvetteforum.com/show...p?p=1550748066
in c2 section
i bypassed the valve/switch on my 67 galaxie.
Years ago, 1990, i had a rear leak and lost ALL brakes
even pumping gave nothing. NOW it has adequate brakes w/1 open bleeder.
the pedal is lower, but firm, and can lock the wheels.
see current topic
http://forums.corvetteforum.com/show...p?p=1550748066
in c2 section
Last edited by Matt Gruber; May 15, 2005 at 08:48 AM.
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Melting Slicks
Joined: Feb 2003
Posts: 3,053
Likes: 4
St. Jude Donor '03,'11
Matt,
You said this in the c2 sect.
"i bought a new GM MC 5-19-76 for $16.85 for my 61. still works great.
in 2 other cars with so called dual braking, i've had complete loss of brakes(with just 1 leak)"
What does the MC come from, a truck? I've been looking for a disk brake master with a 1.25 bore that will fit our cars.
.
You said this in the c2 sect.
"i bought a new GM MC 5-19-76 for $16.85 for my 61. still works great.
in 2 other cars with so called dual braking, i've had complete loss of brakes(with just 1 leak)"
What does the MC come from, a truck? I've been looking for a disk brake master with a 1.25 bore that will fit our cars.
.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Originally Posted by turtlevette
Matt,
You said this in the c2 sect.
"i bought a new GM MC 5-19-76 for $16.85 for my 61. still works great.
in 2 other cars with so called dual braking, i've had complete loss of brakes(with just 1 leak)"
What does the MC come from, a truck? I've been looking for a disk brake master with a 1.25 bore that will fit our cars.
.
You said this in the c2 sect.
"i bought a new GM MC 5-19-76 for $16.85 for my 61. still works great.
in 2 other cars with so called dual braking, i've had complete loss of brakes(with just 1 leak)"
What does the MC come from, a truck? I've been looking for a disk brake master with a 1.25 bore that will fit our cars.
.
Melting Slicks
Joined: Feb 2003
Posts: 3,053
Likes: 4
St. Jude Donor '03,'11
Originally Posted by norvalwilhelm
I thought a stock power master cylinder for our cars was 1 1/4 inch bore and the manual master was 1 inch????????
Either a 1.00 inch or 1.125 inch.
only trucks had 1.25 inch.
Thread Starter
Instructor
Joined: Feb 2004
Posts: 210
Likes: 0
From: woodstock ga
should i remove the valve?
does it truly improve performance?
I have semimetalic pads with a new mc and brake booster , new front calipers and rebuild rears. it doesent feel like it has enough bite. the pedal does not have enough feel to it.
does it truly improve performance?
I have semimetalic pads with a new mc and brake booster , new front calipers and rebuild rears. it doesent feel like it has enough bite. the pedal does not have enough feel to it.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Originally Posted by scotty13
should i remove the valve?
does it truly improve performance?
I have semimetalic pads with a new mc and brake booster , new front calipers and rebuild rears. it doesent feel like it has enough bite. the pedal does not have enough feel to it.
does it truly improve performance?
I have semimetalic pads with a new mc and brake booster , new front calipers and rebuild rears. it doesent feel like it has enough bite. the pedal does not have enough feel to it.
I would not hesitate to get rid of it. It does more harm then good.
Drifting
Joined: Oct 2004
Posts: 1,259
Likes: 7
From: Ontario
Originally Posted by scotty13
should i remove the valve?
does it truly improve performance?
I have semimetalic pads with a new mc and brake booster , new front calipers and rebuild rears. it doesent feel like it has enough bite. the pedal does not have enough feel to it.
does it truly improve performance?
I have semimetalic pads with a new mc and brake booster , new front calipers and rebuild rears. it doesent feel like it has enough bite. the pedal does not have enough feel to it.
Last edited by Retro78; May 16, 2005 at 03:41 PM.
Drifting
Joined: Oct 2004
Posts: 1,259
Likes: 7
From: Ontario
Originally Posted by greyghost79
how do you "join" all the lines together if you remove it?
Last edited by Retro78; May 17, 2005 at 10:58 AM.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Originally Posted by carguy4sure
Norval suggested to either obtain two connecting brass blocks(front & rear) with whatever adapters required for your line/thread sizes, or to fabricate a single new block out of a piece of brass that keeps both front and rear isolated. The fabrication is not that bad, basically drilling holes and tapping with the correct brake lines flare adapters. I just took my valve out tonight and will let you know what I end up doing. Tomorrow evening I am going over to Norval's shop, we are going to see if there is even an easier way by modifying the stock valve..as in sealing off the valve with a brass plug.
Le Mans Master
Joined: Mar 2001
Posts: 6,638
Likes: 287
From: Ann Arbor Michigan
Norval,
There is a way to disable the proportioning section of the valve and still have it function as a differential pressure warning device (RED brake failure light). If you have the type of valve I described in an eariler post (2 attaching bolts mounted horizontally under the M/C), remove the rear brake tube from the valve. Remove the large hex shaped end plug it was screwed into (no parts will fly out). You will see a rubber stopper looking thing stuck in the end of the piston. Pull this piece out (I believe there is a e'ring holding it in with a small spring behind it. remove the spring also). Screw the large hex plug back in. Connect the rear brake line and bleed the system. The rubber stopper is the "valve seat" that causes the valve to proportion. Without it, it's just a junction block. I'm trying to get a hold of one of these old Weatherhead valves so I can take some pictures for everyone since there seems to be much confusion as what it actually does. Everyone just needs to be warned that removing the prop valve may result in stability problems in a panic stop.
There is a way to disable the proportioning section of the valve and still have it function as a differential pressure warning device (RED brake failure light). If you have the type of valve I described in an eariler post (2 attaching bolts mounted horizontally under the M/C), remove the rear brake tube from the valve. Remove the large hex shaped end plug it was screwed into (no parts will fly out). You will see a rubber stopper looking thing stuck in the end of the piston. Pull this piece out (I believe there is a e'ring holding it in with a small spring behind it. remove the spring also). Screw the large hex plug back in. Connect the rear brake line and bleed the system. The rubber stopper is the "valve seat" that causes the valve to proportion. Without it, it's just a junction block. I'm trying to get a hold of one of these old Weatherhead valves so I can take some pictures for everyone since there seems to be much confusion as what it actually does. Everyone just needs to be warned that removing the prop valve may result in stability problems in a panic stop.