modifying proportioning valve for rear disc?
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Lead Driver
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From: West Virginia
modifying proportioning valve for rear disc?
I've seen several posts in searches where people talk about drilling out the residual valve on the proportioning valve, but I cannot find anywhere that actually shows where the residual valve is or how to drill it out.
Basically, from reading the forum posts, there is a 10 lb residual valve on the rear lines, which retains about 10 lbs of pressure on your rear line even when you are not using the brakes. I've heard if you keep this with discs, it will lightly rub the pads against the rotors at all times, wearing them prematurely and possible glazing them over.
Some people on here report going to discs and making no changes and being fine with it, and in fact I called jeff's bronco graveyard about their disc swap and he said they recommend leaving the valve alone but installing an adjuster in line adjust the rear line pressure to make sure the rears don't lock up before the fronts. He said most people just run as is.
Anyone have any experience either way?
Basically, from reading the forum posts, there is a 10 lb residual valve on the rear lines, which retains about 10 lbs of pressure on your rear line even when you are not using the brakes. I've heard if you keep this with discs, it will lightly rub the pads against the rotors at all times, wearing them prematurely and possible glazing them over.
Some people on here report going to discs and making no changes and being fine with it, and in fact I called jeff's bronco graveyard about their disc swap and he said they recommend leaving the valve alone but installing an adjuster in line adjust the rear line pressure to make sure the rears don't lock up before the fronts. He said most people just run as is.
Anyone have any experience either way?
Fleet Owner
Joined: Dec 2009
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From: NorCal
Experience? You bet.
I did an SSBC disc brake retrofit on my 65 Stang and am using a Wilwood prop valve. On the 68 Stang, it has a Granada swap with disc/drum combo valve/booster/ MC from Master Power Brakes. On my project 70 Bump, I'm ditching the 78 donor's prop valve and going with a Wilwood prop valve... much simpler to install, relocates it from the inside frame rail to under the MC, and I dont' have to worry about that stupid pin popping out or the internal piston errantly activating the brake light.
Residual valves are only required when the MC is mounted lower than the calipers like in under-floor mounted MCs in some customs and hot rods. In those cases, it's 2 lb for the front discs and a 10 lb for the rear drum brakes.
I would not modify the stock prop valve but rather get rid of it altogether.
I did an SSBC disc brake retrofit on my 65 Stang and am using a Wilwood prop valve. On the 68 Stang, it has a Granada swap with disc/drum combo valve/booster/ MC from Master Power Brakes. On my project 70 Bump, I'm ditching the 78 donor's prop valve and going with a Wilwood prop valve... much simpler to install, relocates it from the inside frame rail to under the MC, and I dont' have to worry about that stupid pin popping out or the internal piston errantly activating the brake light.
Residual valves are only required when the MC is mounted lower than the calipers like in under-floor mounted MCs in some customs and hot rods. In those cases, it's 2 lb for the front discs and a 10 lb for the rear drum brakes.
I would not modify the stock prop valve but rather get rid of it altogether.
Laughing Gas
Joined: Dec 2007
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From: Alvarado, TX
I ditched the stock prop valve and ran a Wilwood adjustable on the rear line while the fronts are straight off the MC. It's worked great with both the chevy calipers on the old D60 and now the dual piston calipers on the Sterling.
Senior User
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I went with the 4 wheel disk proportioning valve from wildhorses4x4
Proportioning Valve - WILD HORSES Early Ford Bronco Parts
Proportioning Valve - WILD HORSES Early Ford Bronco Parts
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All rear drum brake master cylinders have a residual valve, regardless of mounted location. It is usually behind the brass press-in fitting in the forward reservoir.
I should say "usually" as I have done 3 different conversions and 1 of the master cylinders did not have the the rubber valve in place.
As was stated you would need a stronger residual valve if the M/C was located lower than the rest of the brake system.
Josh
I should say "usually" as I have done 3 different conversions and 1 of the master cylinders did not have the the rubber valve in place.
As was stated you would need a stronger residual valve if the M/C was located lower than the rest of the brake system.
Josh
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Lead Driver
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From: West Virginia
I should have mentioned, I like the factory proportioning valve because it has the pin, so if I do lose pressure on one end, I will still keep some bit of pressure on the other end. I'd really like to keep this feature. Besides, my stock one appears to be working ok, so I don't really want to spend money replacing it with an aftermarket one, especially since I'm running all brand new stainless steel hard lines from inline tube that have the factory fittings on them.
82 Gt: The one from iron horse appears to be the same as the one JBG sells, and they told me the '77 bronco one is different than the '78 F150, they said they are not interchangeable and use different size fittings. They put me on hold for like 15 minutes while the 2 guys talked it over and thats what they said. I have 0 experience with early bronco stuff so I have no idea if thats true. From the picture it certainly looks the same.
are you running stock lines?
82 Gt: The one from iron horse appears to be the same as the one JBG sells, and they told me the '77 bronco one is different than the '78 F150, they said they are not interchangeable and use different size fittings. They put me on hold for like 15 minutes while the 2 guys talked it over and thats what they said. I have 0 experience with early bronco stuff so I have no idea if thats true. From the picture it certainly looks the same.
are you running stock lines?
Senior User
Joined: Jul 2009
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82 Gt: The one from iron horse appears to be the same as the one JBG sells, and they told me the '77 bronco one is different than the '78 F150, they said they are not interchangeable and use different size fittings. They put me on hold for like 15 minutes while the 2 guys talked it over and thats what they said. I have 0 experience with early bronco stuff so I have no idea if thats true. From the picture it certainly looks the same.
are you running stock lines?
are you running stock lines?
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Junior User
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Maybe I missed it, but what kind of MC do you need to get to replace the stock MC designed for rear drums?
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Lead Driver
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From: West Virginia
Apparently, according to the "experts" at jbg and a few other people on the forums, many people run the stock disc/drum mc and prop valve and it works just fine for their disc swap. Even when changing the prop valve I think most people leave the mc stock. There may be a difference in the older drum/drum mc's, in fact, I'm betting that there is. Again, from what I've read, most people that are upgrading try to get their booster and MC off a 79 F350, as they claim this is the strongest. IIRC, the 79 F350 sticks out a bit more as well. Its got a thicker booster.
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Apparently, according to the "experts" at jbg and a few other people on the forums, many people run the stock disc/drum mc and prop valve and it works just fine for their disc swap. Even when changing the prop valve I think most people leave the mc stock. There may be a difference in the older drum/drum mc's, in fact, I'm betting that there is. Again, from what I've read, most people that are upgrading try to get their booster and MC off a 79 F350, as they claim this is the strongest. IIRC, the 79 F350 sticks out a bit more as well. Its got a thicker booster.
And I only used the Ranger master cylinders for the somewhat "bling" factor of the aluminum.
Josh
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Josh
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From: West Virginia
which hydroboost did you guys use? My local junkyard has started getting in medium duty trucks and there are a ton of hydroboosts to choose from. What I found is that a number of them appear to work opposite of the stock ford booster, in that the pedals are set up so there is a pivot between the pedal and the rod to the booster, so pulling the rod OUT towards the driver is what actuates the booster! Weird setup. I did find one off a late 80's maybe early 90's box chevy 3500 box truck that I will have to drill the firewall to install, but uses the same bolt pattern as my stock MC. Idk, I've done a lot of reading up on other conversions but haven't seen a whole lot for specific installs on the 70's ford trucks. Do you guys have any links to the set up you used or install threads? I'd love to see em!
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From: Costa Mesa, CA
The F-450 trucks from the late 90's into the 2000's and then the super-dookie trucks are what is used most I believe. My units are both off 2000-2001 super-dookies. Chevy astro van units are also popular, but any unit can pretty much be made to work. There's quite a few threads on here already about the hydro swaps.