Which Proportioning valve for 4 wheel disc

I got prebent brake line kit from Dante's (inline tube) back in September for my '73 barracuda. Not only do the bends not match the configuration of my valve but the fittings are different sizes. I realized the valve on the car is probably for drum/drum. Not to mention this was a drag car so there's no telling what valve I have.
Can someone give me a part number of wher I need ?
Thanks

Can of worms type of question. You don't need a prop valve with 4 wheel disc brakes since you don't have rear drums. The prop valve "blows off" the pressure to the rear drums so they don't lock up. Drum brakes are non-linear while disc brakes are linear which is why the rear drums need the blow off valve.

Now having said that, lots of people do put a prop valve in a 4 wheel disc setup so they can adjust the rear braking. But that only works if the car is set up with a rear bias to start with. If the car has a front bias on the brakes and you dial down the rears even further then all you are doing is killing the brake effectiveness.

Confused yet?

Bottom line nobody can tell you what to do since we have no idea what you're working on. To properly design a 4 wheel disc system you need to know the weight distribution of the car and the types of brakes and what the static proportioning is front to rear and bunch of stuff like that.

Yeah, I don't either and all of that just blew right over my head. But I have stock single piston calipers on the front with 11" discs with el budget disc on the rear. The master cylinder is stock style with two resivoir.
I haven't considered creating a bias and honestly I'm not sure I would since I'll really just be cruising.
This is helping though and maybe you can help me get them working ! But if I don't need the valve, can I plumb them front/front , rear/rear and get braking without the valve?

You could start by carefully adjusting the bends, then replace the fittings on the new lines with the correct ones for your existing valve. I would assume that as long as you have a decent master cylinder and a distribution valve it should work. I have recently learned that there is a hold off valve for the back brakes on later models with 4 wheel disc brakes. In lieu of that adding a proportioning valve would also give you the opportunity to fine tune the system if you have to. I know it is a pain to change them but what I also always do; is make sure that the master cylinder has the word "disc" somewhere in the description when converting to disc brakes as well. I'm sure it is better to have more than less, so when it comes to brakes, I think its the only time that wearing a belt and suspenders makes sense.

What car has a hold-off valve with rear disks? I don't remember seeing this ever. My family happened to own some non-ABS rear disk cars (GM W-bodies) and there is no valve of any kind present.

Now going to personal experience from swapping from 11.75 disk front and 10x2.5" drum rear to the Dr Diff Mustang Cobra 13" Front Disk and 11.75" Disk rear that I opened my adjustable proportioning valve completely and there is absolutely no brake bias issue of any kind.

Not sure what rear disks you bought but if they are the Olds Toronado calipers I usually see on budget ones, the pistons might be a little bigger than they need to be. An adjustable valve and nothing else (other than maybe a drum distribution block to make the tees) should be fine.

Simple answer to "what prop valve is needed with 4 wheel discs" is usually none. Just get the pressure to front and rear w/o restriction as a starting point. Then see how it does.

I actually agree with the whole just put it together and go...see what happens. I'd rather see the extra parts in the system before it is filled and bled though... taking it apart again it is messy and bleeding the system can be challenging at times. I looked up the rear hold off valve and found that it came on "all 67-70 cars with the Kelsy Hayes 4 wheel disc brake option and high performance engines". I converted a 69 roadrunner front wheel discs, using a disc drum master without a purportioning valve and it worked great. This time around I"ll be adding one as I cut the rear break line while relacing the front frame rail. I have one and figure it to be an easy way to splice the line and have it if I need it.

Yes you can just plumb together what you have to get it going. But be very careful since what you describe is most likely dangerous in a panic stop or on a wet road.

If the brake system isn't properly designed then it isn't going to work very well under panic stop situations. It will work just fine for normal driving but if a semi truck pulls out in front of you when you're going 90 mph on a back road then that might be the last we'll hear of you.

AndyF is spot on. A properly designed 4 wheel disc system doesn't need a p valve. We need more information on your conversion.

That said, I'd plumb the fronts straight to the master, I'd add an adjustable valve to the rear. Remove any residual pressure valve. You can use a drum drum or disc drum master but you need to keep an eye on fluid level. Disc units have larger reservoirs to accommodate the make up fluid as pads wear vs the drum adjuster to accommodate shoe wear.

Andy F is correct. The proportioning valve limits maximum pressure to the rear brakes so they don't prematurely lock-up . Once the rear lock-up in a panic stop it can cause directional instability (car goes sideways).

With a properly designed 4-wheel disc brake set-up (disc sizing and friction material) and a properly balanced vehicle, a prop valve is not required and may increase stopping distance.

A further consideration is that you may already have a prop valve incorporated in your combination valve. If they car came from the factory with front disc and rear drum, and the car has the factory combo valve, then it's possible a prop valve is already installed.

Which you should correct before you start bending on those shiney new lines. If your car came with disc/drum proportioning valve you need to get a drum/drum distribution block which has a different hard line routing and may acount for why your custom lines don't fit. I know Dr.Diff sells them, I'm sure there are other sources as well.

On our 71 Barracuda I used the pedal, booster, master cylinder, calipers and rotors from a 2016 Hellcat Charger. I used a Wildwood proportioning valve and bent my own 3/16th brake line. I also used the e brake cable and assembly from the Charger. I haven't got the engine wired yet so I can't tell you if the brakes will work, but those 6 piston Brembo's and 15 inch rotors should get the job done.

There are no 4 wheel disc brake cars from 67-70, unless you are talking about a different manufacturer.

A hold off valve is used in disc/drum systems to prevent pressure to the discs until a set pressure is generated int he rear system. this is to overcome the spring pressure holding hte shoes in place and overcome the very slight gap between the shoes and drum. Theoretically, this would allow the shoes and pads to apply simultaneously.

The hold off valve is not used in a 4 wheel disc system.

The Imperial had 4 wheel disc brakes for a few years using A body calipers on the rear. I've only seen one of those setups in the wrecking yard and I didn't look to see what they used for valving. Not sure if the factory used a prop valve or just a combination valve when they designed that setup.

Then why dont we use A body disc brakes on the rear of an 8 3/4?

so, if a person has all new wilwood 12.19 brakes with the dynapro 4 piston calipers on all 4 corners, wouldn't a wilwood master cylinder and prop valve kit be good to go? something like this? vvv

https://www.summitracing.com/parts/wil-261-13269

this is what I plan to use, please tell me I could be okay? This is a small block A body car, street/strip.

Why don't you look into that and tell us why.

That's what I have [6piston front/4rear], figure out what bore you want, however.

If you have the same rotors and calipers on all four corners you'll be in a world of hurt in a panic stop. I'm not sure a prop valve is going to be able to save you.

well I'll be damned. I bought all this stuff quite a while ago. Now I'm finally putting everything together. LOL. I guess, if nothing else, I could go to a 13 or 14 inch rotor on the front, along with a 6 piston caliper. Would you say that will maybe solve my predicament? And by definition of the word, "a difficult, unpleasant, or embarrassing situation" is exactly how I feel now...

Also I might add, after a little bit of reading, that I was wrong in stating ALL calipers were the same size...the rears still have 4 pistons, but they are a smaller diameter piston than the front.

I think your setup will work just fine. I used a Wildwood proportioning valve with my 4 wheel disk setup. I'll leave it wide open to start and if I need more bias I'll adjust it. I would rather have it just in case as opposed to needing it and not have it.