Proportion valve

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Robsweden

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My Car
Mach 1 73 351c
Hello

Im going for rear discbrakes.  Im currently having disc in the front and drums in the rear. Should change the block with built in propotion fixed valve, or just buy an adjustable valve and connect it on the rear brakeline ?





Regards Rob

 
Robsweden,

I would go with the second one. It has the pressure switch connector. The first one would be used more in a track environment that would provide more granular control over the pressure from front to back.

 
From what I did to my car, still with drum rears, I have an adjustable valve on the REAR circuit only, meaning I have 2 separate circuits. These cars are soooo light on the rear end, they lock up the wheels way to easily, even with a trac-loc dif. Mine happens to be an open dif, but without being able to adjust the pressure, the left wheel (un-driven) locks up in an instant. With disc brakes on the rear, I would think they could lock up even easier.

Another reason I like having 2 separate brake circuits is personal. I have had TWO major brake failures in my lifetime, one being in my 72 Q code Mach 1 which could have been fatal if not for quick reactions on my part. Fortunately I saved the car from wrecking. I would have had a chance to stop the car if I only had braking to the rears.

 
I kept the stock combination valve/distribution block and added the adjustable valve. The only reason I kept the block is to keep use of the idiot light. However, I removed the proportioning plunger of the stock combination valve so not to have two adjusting valves acting in series.

See thread:

https://www.7173mustangs.com/thread-connecting-an-adjustable-proportioning-valve-to-stock-distribution-block?page=3
Click to expand...
 That's more or less what I did, but I found the idiot light switch no longer works, light on all the time. I left it un-connected. So, would removing the prop. plunger fix that issue? All I did was plug off the rear line connectors on the block.

 
I kept the stock combination valve/distribution block and added the adjustable valve. The only reason I kept the block is to keep use of the idiot light. However, I removed the proportioning plunger of the stock combination valve so not to have two adjusting valves acting in series.

See thread:

https://www.7173mustangs.com/thread-connecting-an-adjustable-proportioning-valve-to-stock-distribution-block?page=3
Click to expand...
 That's more or less what I did, but I found the idiot light switch no longer works, light on all the time. I left it un-connected. So, would removing the prop. plunger fix that issue? All I did was plug off the rear line connectors on the block.
Click to expand...
I don't know if removing the plunger/spring will make the switch work. In mine it always worked, but I had to be careful when assembling it that it was centered. If you disassemble the valve and move the switch manually, does it work? Also, you say that you just plugged off the rear line connector. Did the light switch issue started after this? The light switch works on pressure differential so if you plug the rear line connector I wonder if the switch is not self centering to turn the light off. It may be staying displaced to one side, and such, keep the light on.

 
I kept the stock combination valve/distribution block and added the adjustable valve. The only reason I kept the block is to keep use of the idiot light. However, I removed the proportioning plunger of the stock combination valve so not to have two adjusting valves acting in series.

See thread:

https://www.7173mustangs.com/thread-connecting-an-adjustable-proportioning-valve-to-stock-distribution-block?page=3
Click to expand...
 That's more or less what I did, but I found the idiot light switch no longer works, light on all the time. I left it un-connected. So, would removing the prop. plunger fix that issue? All I did was plug off the rear line connectors on the block.
Click to expand...
I don't know if removing the plunger/spring will make the switch work. In mine it always worked, but I had to be careful when assembling it that it was centered. If you disassemble the valve and move the switch manually, does it work? Also, you say that you just plugged off the rear line connector. Did the light switch issue started after this? The light switch works on pressure differential so if you plug the rear line connector I wonder if the switch is not self centering to turn the light off. It may be staying displaced to one side, and such, keep the light on.
Click to expand...
 Tony, yes it worked before I disconnected the rear lines and plug them off, so obviously it needs both circuits pressurized to work. I think you are right that the switch is not self centering. It would be nice to know that at least my front brakes are good. Not sure what to do or even if it's worth looking at now as it would be a lot of work.

Thanks for your input.

Geoff.

 
 That's more or less what I did, but I found the idiot light switch no longer works, light on all the time. I left it un-connected. So, would removing the prop. plunger fix that issue? All I did was plug off the rear line connectors on the block.
Click to expand...
I don't know if removing the plunger/spring will make the switch work. In mine it always worked, but I had to be careful when assembling it that it was centered. If you disassemble the valve and move the switch manually, does it work? Also, you say that you just plugged off the rear line connector. Did the light switch issue started after this? The light switch works on pressure differential so if you plug the rear line connector I wonder if the switch is not self centering to turn the light off. It may be staying displaced to one side, and such, keep the light on.
Click to expand...
 Tony, yes it worked before I disconnected the rear lines and plug them off, so obviously it needs both circuits pressurized to work. I think you are right that the switch is not self centering. It would be nice to know that at least my front brakes are good. Not sure what to do or even if it's worth looking at now as it would be a lot of work.

Thanks for your input.

Geoff.
Click to expand...
The idiot light is just "idiot" since you won't know if you have a brake failure until you press the pedal.

 
What I did...

Personally I run an adjustable prop valve on everything I have that does not have ABS brakes.

Click to expand...
What master cylinder are you using?

 
What I did...

Personally I run an adjustable prop valve on everything I have that does not have ABS brakes.

Click to expand...
What master cylinder are you using?
Click to expand...
2000 Ford Mustang V6 without traction control.  It is 1" bore - only think that isn't ideal is that the ports are on the wrong side.  I have disks front and rear.

 
What I did...

Personally I run an adjustable prop valve on everything I have that does not have ABS brakes.

Click to expand...
What master cylinder are you using?
Click to expand...
2000 Ford Mustang V6 without traction control.  It is 1" bore - only think that isn't ideal is that the ports are on the wrong side.  I have disks front and rear.
Click to expand...
 
I also have the V6 master cylinder with aftermarket proportioning valve like the Wilwood shown. With stock front discs & rear drums I have had to turn the prop valve all the way closed and depending on what tyres I have on the rear they still lock up first sometimes. Anyone got ideas on how to improve this?

 
I also have the V6 master cylinder with aftermarket proportioning valve like the Wilwood shown. With stock front discs & rear drums I have had to turn the prop valve all the way closed and depending on what tyres I have on the rear they still lock up first sometimes. Anyone got ideas on how to improve this?
Click to expand...
Do you have the forward MC port plumbed to your rear brakes and the rear MC port plumbed to your front brakes?

Drum brakes are more efficient than disk brakes, you might have to swap your rear drums for disks if you want your MC / prop valve to work.

 
I also have the V6 master cylinder with aftermarket proportioning valve like the Wilwood shown. With stock front discs & rear drums I have had to turn the prop valve all the way closed and depending on what tyres I have on the rear they still lock up first sometimes. Anyone got ideas on how to improve this?
Click to expand...
Have you made sure that there is not a residual pressure valve in the rear outlet port of the master cylinder? It is a spring loaded neoprene "piston" under the brass seat in the rear brake outlet of the master cylinder. If it is still there, the rear disc brakes will be preloaded at 10 PSI causing the rears to engage more quickly (or drag) than the fronts. Chuck

 

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