Title: Prop valve question
Post by: Thunder Chicken on April 01, 2007, 01:21:28 PM
Post by: Thunder Chicken on 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:
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:
Title: Prop valve question
Post by: EricCoolCats on April 01, 2007, 10:34:45 PM
Post by: EricCoolCats on 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.
Title: Prop valve question
Post by: Thunder Chicken on April 01, 2007, 10:50:28 PM
Post by: Thunder Chicken on 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)?
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)?
Title: Prop valve question
Post by: slicksport88 on April 02, 2007, 03:38:06 PM
Post by: slicksport88 on 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.
Title: Prop valve question
Post by: Thunder Chicken on April 02, 2007, 04:05:31 PM
Post by: Thunder Chicken on 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)?
Title: Prop valve question
Post by: Red_LX on April 02, 2007, 04:16:18 PM
Post by: Red_LX on 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.
Title: Prop valve question
Post by: slicksport88 on April 02, 2007, 05:30:20 PM
Post by: slicksport88 on 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;137819
Did that adapter thread into the proportioning valve where the plug is in my car (and the switch is in TC's)?
Title: Prop valve question
Post by: Red_LX on April 02, 2007, 08:34:27 PM
Post by: Red_LX on 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.
Title: Prop valve question
Post by: Jim_Miller on May 10, 2007, 01:21:09 PM
Post by: Jim_Miller on 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.
Title: Prop valve question
Post by: 32VFoxBird on May 10, 2007, 01:29:42 PM
Post by: 32VFoxBird on May 10, 2007, 01:29:42 PM
i have this pic, if it helps:
Title: Prop valve question
Post by: Jim_Miller on May 10, 2007, 01:37:54 PM
Post by: Jim_Miller on 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?
“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?
Title: Prop valve question
Post by: Jim_Miller on May 10, 2007, 01:38:43 PM
Post by: Jim_Miller on May 10, 2007, 01:38:43 PM
Quote from: 32VFoxBird;146241
i have this pic, if it helps:
what pic?
Anything will help
Title: Prop valve question
Post by: Thunder Chicken on May 10, 2007, 01:56:16 PM
Post by: Thunder Chicken on 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.
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.
Title: Prop valve question
Post by: Red_LX on May 10, 2007, 02:27:54 PM
Post by: Red_LX on 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.
Title: Prop valve question
Post by: Chuck W on May 10, 2007, 02:36:42 PM
Post by: Chuck W on 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.
Title: Prop valve question
Post by: dudeman351 on May 12, 2007, 08:45:29 PM
Post by: dudeman351 on May 12, 2007, 08:45:29 PM
that pressure switch is for the suspension in th TC. under hard braking it turns on the firm setting when in auto mode.
Title: Prop valve question
Post by: thundr306 on May 29, 2007, 09:09:57 PM
Post by: thundr306 on May 29, 2007, 09:09:57 PM
I think this is the valve that you are talking about off the sn95. Couldn't I just use this valve and no aftermarket rear proportioning valve since it came off a disc/disc car?
(http://thumb13.webshots.net/t/53/753/9/60/74/2776960740100929333hvwRqM_th.jpg) (http://good-times.webshots.com/photo/2776960740100929333hvwRqM)
(http://thumb13.webshots.net/t/57/657/5/10/27/2255510270100929333qHYlSI_th.jpg) (http://good-times.webshots.com/photo/2255510270100929333qHYlSI)
(http://thumb13.webshots.net/t/53/753/9/60/74/2776960740100929333hvwRqM_th.jpg) (http://good-times.webshots.com/photo/2776960740100929333hvwRqM)
(http://thumb13.webshots.net/t/57/657/5/10/27/2255510270100929333qHYlSI_th.jpg) (http://good-times.webshots.com/photo/2255510270100929333qHYlSI)
Title: Prop valve question
Post by: Prototype Services on May 29, 2007, 11:35:10 PM
Post by: Prototype Services on May 29, 2007, 11:35:10 PM
Guys, let me offer an opinion.
It seems a lot of us are swappping around brake stuff, converting to bigger, better brakes. Obviously some using OEM parts, some with aftermarket. Some a combination of the two.
There is a certain percent of difference built into the braking system of any car; front to rear. Fronts can have up to 100% of the braking force. Ever see a sportbike up on it's front wheel under braking? That is 100% weight transfer with ALL the braking being done by the front.
It is easy to get the designed ratio off when swapping components. It can be anything from annoying to dangerous.
Drum brakes are "self-energizing" meaning the rotation of the drum helps "pull" the brake shoes into the drum, increasing braking force. This is why there is a delay built into the system with the rear drums.
Getting this "ratio" right when swapping discs is made much easier by simply "teeing" the front lines and adding an aftermarket proportioning valve in the rear line so you can adjust the amount of rear brake force used. You ALWAYS want the fronts to lock up first.
I think Gumby showed, in a recent post, the best and easiest way to plumb a modified braking system.
Just my $.02
Dave
It seems a lot of us are swappping around brake stuff, converting to bigger, better brakes. Obviously some using OEM parts, some with aftermarket. Some a combination of the two.
There is a certain percent of difference built into the braking system of any car; front to rear. Fronts can have up to 100% of the braking force. Ever see a sportbike up on it's front wheel under braking? That is 100% weight transfer with ALL the braking being done by the front.
It is easy to get the designed ratio off when swapping components. It can be anything from annoying to dangerous.
Drum brakes are "self-energizing" meaning the rotation of the drum helps "pull" the brake shoes into the drum, increasing braking force. This is why there is a delay built into the system with the rear drums.
Getting this "ratio" right when swapping discs is made much easier by simply "teeing" the front lines and adding an aftermarket proportioning valve in the rear line so you can adjust the amount of rear brake force used. You ALWAYS want the fronts to lock up first.
I think Gumby showed, in a recent post, the best and easiest way to plumb a modified braking system.
Just my $.02
Dave
Title: Prop valve question
Post by: booksix on October 26, 2007, 09:21:13 PM
Post by: booksix on October 26, 2007, 09:21:13 PM
resurrecting this one.... I currently have:
Cobra 2 port M/C. 1 line feeding prop valve 'front' and one line feeding prop valve 'rear'. The prop valve is gutted and the 'front' line, which should now flow straight through the gutted valve (making is just a union) splits with a T after the stock valve and goes to both front brakes. The 'rear' line comes off the stock valve to a wilwood prop valve before going to the rear and splitting.
I want to eliminate the stock prop valve but a few ppl on various fox car forums say NO. But in all reality, it's completely pointless on my setup.... am I missing something?
Cobra 2 port M/C. 1 line feeding prop valve 'front' and one line feeding prop valve 'rear'. The prop valve is gutted and the 'front' line, which should now flow straight through the gutted valve (making is just a union) splits with a T after the stock valve and goes to both front brakes. The 'rear' line comes off the stock valve to a wilwood prop valve before going to the rear and splitting.
I want to eliminate the stock prop valve but a few ppl on various fox car forums say NO. But in all reality, it's completely pointless on my setup.... am I missing something?
Title: Prop valve question
Post by: booksix on October 27, 2007, 04:18:35 PM
Post by: booksix on October 27, 2007, 04:18:35 PM
well, idk.. I'm gonna give it a shot. I dont know why it'd be necessary...
Title: Re: Prop valve question
Post by: Driverguy on May 16, 2021, 05:14:28 PM
Post by: Driverguy on May 16, 2021, 05:14:28 PM
Resurrecting this, as this seems to be the closest thread to my needs...If I am doing the same sn95 master cylinder upgrade as O/P, in an attempt to reduce mushy pedal after my 11" brake upgrade, AND I am converting to rear discs, could I use an SN95 2 in, 3 out prop valve? My only other options being modifying a turbo coupe prop valve, as OP may have done, or just getting a wilwood 2 in, 3 out prop valve. I'm not opposed to a wilwood prop valve, i just thought it may be a very easy solution to swap out my stock valve for an SN-95 and mount it in the same place, not have to remake any lines, potentially.
Title: Re: Prop valve question
Post by: Driverguy on May 16, 2021, 05:15:21 PM
Post by: Driverguy on May 16, 2021, 05:15:21 PM
(https://i.ebayimg.com/images/g/z4EAAOSwW~JcUWZg/s-l1600.jpg)
Title: Re: Prop valve question
Post by: gtbird on May 17, 2021, 07:40:14 AM
Post by: gtbird on May 17, 2021, 07:40:14 AM
I have an NOS prop valve from 87-88 T/C available for sale if interested.
Rick
Title: Re: Prop valve question
Post by: Driverguy on May 17, 2021, 06:21:45 PM
Post by: Driverguy on May 17, 2021, 06:21:45 PM
is it 2 in, 3 out??
Title: Re: Prop valve question
Post by: gtbird on May 17, 2021, 08:41:53 PM
Post by: gtbird on May 17, 2021, 08:41:53 PM
It has 2 ports top and 2 on the bottom.
Title: Re: Prop valve question
Post by: Driverguy on May 18, 2021, 11:04:24 PM
Post by: Driverguy on May 18, 2021, 11:04:24 PM
wont work, i need 2 in, 3 out
Title: Re: Prop valve question
Post by: QUICKSHIFT on May 20, 2021, 05:05:42 PM
Post by: QUICKSHIFT on May 20, 2021, 05:05:42 PM
https://www.summitracing.com/parts/wil-260-11179 This worked for me. Bolted in directly and the lines still connected. I did the 11" on the front and I kept my rear drums with Porterfield shoes and oversized wheel cylinders.
Title: Re: Prop valve question
Post by: Aerocoupe on May 24, 2021, 09:11:45 PM
Post by: Aerocoupe on May 24, 2021, 09:11:45 PM
So any MC you use that has two port you have two choices. First, the combination valve (that is what you have in your picture) a proportioning valve and also has a shuttle valve in it. The shuttle will move to block the front or rear port if you develop a leak in that circuit or at least that is what it is supposed to do by design and then trip the brake light on your dash if the combination valve is so equipped with a switch. The proportioning valve is what decreases the pressure to the rear brakes under heavy braking. Diagram is here with my notes from when I did this on my Mustang and my Bird:
(https://hosting.photobucket.com/albums/yy142/dbrune_83/Car%20Stuff/.highres/BrakeProportioningValveDiagram.jpg?width=1920&height=1080&fit=bounds)
The majority of factory front disc and rear drum Fox cars that I have seen converted to rear disc have had the proportioning valve removed from the front of the combination valve and the front plug replaced with a solid one as the stocker will leak with the proportioning valve removed. This is done to keep the factory shuttle and dash brake light functioning. Replacement end plug is here:
https://www.maximummotorsports.com/Brake-Proportioning-Valve-Plug-1979-2004-P1411.aspx
If you plan on deleting the proportioning valve on the factory combination valve then it allows you to leave the factory brake lines from the combination valve to the front and rear brakes alone as they are a bitch to break loose. Typically most folks option for the 1993 Mustang Cobra MC as it has a 1" bore but it is a two port MC like all SN95 MC's. This only poses a problem on I believe the 87 and up Birds and Cougars as they switched to a three port MC in 87 and used it through the 93 year in the Mustangs with the exception of the Cobra. If you have a three port MC then you will need a 3 to 2 conversion kit like this one:
https://www.maximummotorsports.com/Master-Cylinder-Installation-Kit-1993-Cobra1994-95-GT-mc-in-1987-93-Mustang-P673.aspx
Description says 93 Cobra or 94/95 GT MC's but the V6 cars had the vacuum boosted brakes through 98 so those MC's will work as well. Realize the94/95 GT and 94-98 V6 MC's have a 1-1/16" bore so they push more fluid at a lower pressure and can give you a very stiff pedal compared to an MC with a smaller bore. Do a search on this as there are a several posts on this.
So now you have your MC plumbed in and the proportioning valve deleted you still need a manual proportioning valve between the rear brakes and the feed line to them. On the Mustangs they had a really convenient union on the upper right hand side of the firewall and that is where most put their proportioning valve. Bird and Cougars do not have this so use your imagination. I built a bracket and put it right in front of the combination valve for easy adjustment but once you set it you will not move it unless you start messing with brake compounds.
Now you have solved installing a 2 port MC into a factory 3 port MC car with the 3 to 2 kit and a 2 port MC as well as factored in the necessary braking bias change of swapping to rear disc brakes by removing the stock proportioning valve from the combination valve and installing the manual proportioning valve, All this to keep from replumbing brake lines, flaring lines, keeping the stock shuttle valve in the combination valve and keeping the brake warning light in your dash function like factory.
If you don't give a rats ass about the shuttle valve or dash brake light then punt the combination valve, replumb by splitting the front brake port on the MC to the two front calipers, connect the rear brake supply line to the rear port on the MC, and install a manual proportioning valve in the rear brake supply line at a choice of yours. This will require multiple flares and so good knowledge on how to do this as well as bend brake lines so they don't look like ass, secured properly, and in general don't look like ass.
(https://hosting.photobucket.com/albums/yy142/dbrune_83/Car%20Stuff/.highres/BrakeProportioningValveDiagram.jpg?width=1920&height=1080&fit=bounds)
The majority of factory front disc and rear drum Fox cars that I have seen converted to rear disc have had the proportioning valve removed from the front of the combination valve and the front plug replaced with a solid one as the stocker will leak with the proportioning valve removed. This is done to keep the factory shuttle and dash brake light functioning. Replacement end plug is here:
https://www.maximummotorsports.com/Brake-Proportioning-Valve-Plug-1979-2004-P1411.aspx
If you plan on deleting the proportioning valve on the factory combination valve then it allows you to leave the factory brake lines from the combination valve to the front and rear brakes alone as they are a bitch to break loose. Typically most folks option for the 1993 Mustang Cobra MC as it has a 1" bore but it is a two port MC like all SN95 MC's. This only poses a problem on I believe the 87 and up Birds and Cougars as they switched to a three port MC in 87 and used it through the 93 year in the Mustangs with the exception of the Cobra. If you have a three port MC then you will need a 3 to 2 conversion kit like this one:
https://www.maximummotorsports.com/Master-Cylinder-Installation-Kit-1993-Cobra1994-95-GT-mc-in-1987-93-Mustang-P673.aspx
Description says 93 Cobra or 94/95 GT MC's but the V6 cars had the vacuum boosted brakes through 98 so those MC's will work as well. Realize the94/95 GT and 94-98 V6 MC's have a 1-1/16" bore so they push more fluid at a lower pressure and can give you a very stiff pedal compared to an MC with a smaller bore. Do a search on this as there are a several posts on this.
So now you have your MC plumbed in and the proportioning valve deleted you still need a manual proportioning valve between the rear brakes and the feed line to them. On the Mustangs they had a really convenient union on the upper right hand side of the firewall and that is where most put their proportioning valve. Bird and Cougars do not have this so use your imagination. I built a bracket and put it right in front of the combination valve for easy adjustment but once you set it you will not move it unless you start messing with brake compounds.
Now you have solved installing a 2 port MC into a factory 3 port MC car with the 3 to 2 kit and a 2 port MC as well as factored in the necessary braking bias change of swapping to rear disc brakes by removing the stock proportioning valve from the combination valve and installing the manual proportioning valve, All this to keep from replumbing brake lines, flaring lines, keeping the stock shuttle valve in the combination valve and keeping the brake warning light in your dash function like factory.
If you don't give a rats ass about the shuttle valve or dash brake light then punt the combination valve, replumb by splitting the front brake port on the MC to the two front calipers, connect the rear brake supply line to the rear port on the MC, and install a manual proportioning valve in the rear brake supply line at a choice of yours. This will require multiple flares and so good knowledge on how to do this as well as bend brake lines so they don't look like ass, secured properly, and in general don't look like ass.
Title: Re: Prop valve question
Post by: Aerocoupe on May 24, 2021, 09:25:24 PM
Post by: Aerocoupe on May 24, 2021, 09:25:24 PM
One last note, the '93 Cobra MC or the 94/95 Mustang GT MC or the 94-98 Mustang V6 MC will all work with the following brake set ups:
Stock 11" 87-88 TC front brakes and 87-88 style TC rear brakes or SN95 rear brakes
Stock SN95 V6 or GT brakes all the way around
Stock SN95 Cobra front brakes and stock SN95 GT or V6 brakes in the rear
Stock SN95 Cobra brakes all the way around
Couple of things:
I can verify this as I have installed and or helped install all those combinations and they all worked just fine.
The 93 Mustang Cobra unit has SAE threads and the SN95 units are metric so keep that in mind.
All of the SN95 (94-98) rear calipers are identical. The only thing that differentiates the Cobra from the GT/V6 is the caliper bracket. Again, we have gone into detail on this a couple of times on here.
Stock 11" 87-88 TC front brakes and 87-88 style TC rear brakes or SN95 rear brakes
Stock SN95 V6 or GT brakes all the way around
Stock SN95 Cobra front brakes and stock SN95 GT or V6 brakes in the rear
Stock SN95 Cobra brakes all the way around
Couple of things:
I can verify this as I have installed and or helped install all those combinations and they all worked just fine.
The 93 Mustang Cobra unit has SAE threads and the SN95 units are metric so keep that in mind.
All of the SN95 (94-98) rear calipers are identical. The only thing that differentiates the Cobra from the GT/V6 is the caliper bracket. Again, we have gone into detail on this a couple of times on here.