Prop valve question April 01, 2007, 01:21:28 PM I went over to what is left of the parts car TC today (and believe me, what's left ain't pretty - it's been cut in half, burned, and crushed with a front end loader) and retrieved the proportioning valve - believe it or not, it was intact, having been nowhere near the fire.Anyway, when I got the prop valve home I decided to open it up. ON the front brake end there was what appeared to be a switch, but it had rotted away so only the stump was there. I removed the stump and was surprised to find that inside the front brake portion of the prop valve it is nothing but a "splitter". The line comes in from the M/C, there is a chamber, and the line goes out to the right front brake. The chamber also opens to where this switch was. This leads me to the question: Since the '93 Cobra M/C I've ordered will only have two lines, while my stock 'Bird has three, would I be able to get an adapter that would go in where that switch was on the prop valve and connect the left front brake there?The same spot in my Thunderbird's prop valve, BTW, is just a metal plug. A pic to illustrate what I'm talking about: Quote Selected
Prop valve question Reply #1 – April 01, 2007, 10:34:45 PM I've heard that there is an adapter available but I've personally never searched for one. Several people told me they used one. No photos to back it up, sorry. Quote Selected
Prop valve question Reply #2 – April 01, 2007, 10:50:28 PM I've heard about the adapter too, but if one can simply thread a fitting into the front portion of the master cylinder (physically the part that faces the rear of the car) and put the third line in there it would eliminate the need for an adapter and make for a simpler install and more factory appearing look.The thing that struck me as strange is that by all appearances, the front brakes do not need to be connected to the proportioning valve at all. They do not affect operation of the rear brakes in any way, and there are no passages between the two sections. In the stock T-Bird/Cougar three-line M/C, by all appearances, you could remove the line going to the right front wheel, thread it directly into the M/C, and completely bypass the prop valve for the front brakes.I've got all my experience with GM, and in their prop valves a sliding valve is between the front and rear sections - if one side loses pressure, the valve slides all the way to that side and turns on the brake warning light.Another thing that I thought odd: The TC prop valve had a switch on the front portion (again, facing the rear of the car) - I assume this is a pressure switch, since it isn't a pressure differential switch like in the GM design. My car, however, does not have a switch there. I do not see any provisions in my brake system for a low pressure warning switch. I've got the low fluid switch, but that's it. Is that normal in these cars? So if I were to, say, cut a rear brake line, as long as the fluid level was OK, the light would never come on (even though the pedal would go to the floor)? Quote Selected
Prop valve question Reply #3 – April 02, 2007, 03:38:06 PM When I did my cobra brake conversion I used the adapter from a 94 mustang V6 model. Threaded right in with no problems. I can't remember if I took the line fitting but I would just to be on the safe side. I took a pic of mine to show you but I can't get it reduced in size to post it. Hope this helps. Quote Selected
Prop valve question Reply #4 – April 02, 2007, 04:05:31 PM Did that adapter thread into the proportioning valve where the plug is in my car (and the switch is in TC's)? Quote Selected
Prop valve question Reply #5 – April 02, 2007, 04:16:18 PM If I had to guess, that "switch" on the TC prop valve is in fact a pressure switch. Keep in mind that the master cylinder in the TC's uses a motor to build pressure...I'm sure that switch sends a signal to the motor. Quote Selected
Prop valve question Reply #6 – April 02, 2007, 05:30:20 PM It threads into the proportioning valve so that you can hook your left front line into that spot since your converting from a 3 port master cylinder to a 2 port.Quote from: Thunder Chicken;137819Did that adapter thread into the proportioning valve where the plug is in my car (and the switch is in TC's)? Quote Selected
Prop valve question Reply #7 – April 02, 2007, 08:34:27 PM You can also just tee off the rear port of the master cylinder...which is what I did. Quote Selected
Prop valve question Reply #8 – May 10, 2007, 01:21:09 PM Here is a diagram I found of a prop valve like what is on my 88 5.0 bird. This is the non-TC valve with drum rear brakes. Quote Selected
Prop valve question Reply #9 – May 10, 2007, 01:29:42 PM i have this pic, if it helps: Quote Selected
Prop valve question Reply #10 – May 10, 2007, 01:37:54 PM Ok on the Cobra web site (these guys adapt mustang brakes for there Cobras they talk about “Adapter fitting off of the rear of the prop valve?” And here slicksport88 is talking about “adapter from a 94 mustang V6 model” screwing into the back of the prop valve. Where do I get one of these adaptors? They ON a 94 mustang v6 prop valve so I should be able to find one at a u-pull-it? And my Prop Valve has this Shuttle Valve in it. With the Mustang 11” in the front and the Lincoln 11” in the back just using that on my Prop isn’t going to work is it? I may have access to a TC valve, However I’m pretty sure the TC had anti lock, will that make a diff? Quote Selected
Prop valve question Reply #11 – May 10, 2007, 01:38:43 PM Quote from: 32VFoxBird;146241i have this pic, if it helps: what pic?Anything will help Quote Selected
Prop valve question Reply #12 – May 10, 2007, 01:56:16 PM I dunno if the antilock makes a difference with the TC prop valve or not, but I hope not - I used one :hick:Apparently that adapter can be found in SN95 V6 Mustangs. I didn't get one because the local yard would've wanted me to buy the whole prop valve, if they even had a Mustang to get one from. I made an adapter setup similar to what 32VFoxBird did. I'll take pics later one. Remember, in a front disc/rear drum setup there is a delay between when you step on the brakes and when the front brakes actually start to grab (or vice versa) - it's been too long since I was in trade school and actually had to care about the reason why, but I believe it is to allow the rear drums to start braking at the same time the fronts do, or something along those lines. For shiznits and giggles I might dig out my old text books and look it up.With an all disc setup you don't need that delay, which is why I'd imagine the TC prop valve doesn't have the shuttle valve. Its only job is to regulate pressure to the rear brakes. Quote Selected
Prop valve question Reply #13 – May 10, 2007, 02:27:54 PM The ABS function is entirely in the master cylinder on the TC, so the prop valve will work on anything with four wheel disc. Quote Selected
Prop valve question Reply #14 – May 10, 2007, 02:36:42 PM Quote from: Thunder Chicken;146247 Remember, in a front disc/rear drum setup there is a delay between when you step on the brakes and when the front brakes actually start to grab (or vice versa) - it's been too long since I was in trade school and actually had to care about the reason why, but I believe it is to allow the rear drums to start braking at the same time the fronts do, or something along those lines. For shiznits and giggles I might dig out my old text books and look it up.It's the rears...look at your diagram. See the front side with the spring/plunger. That acts as the delay of the line pressure hitting the rear brakes. Quote Selected
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