Exactly right. It doesn’t retain any pressure. The proportioning valve allows free flow back to the master cylinder while restricting flow when the rear brakes are applied.
Bingo!
I have adjustable proportioning valve on the race Cougar. Best way to set it to have pressure gauges for the front and rear to dial it in. With no pressure gauges when I first started to set it at the track I was looking for advise. The seasoned racers told me to increasing the pressure to the rear brakes until you brake hard into a corner and your ass end slides around. Then back it off 1 1/2 turns and you’re good to go 
It’ll be a year from now , my brakes don’t work at all but when I get them done for nothing more than curiosity I’m going to drill out the bottom of a bleeder, braze a fitting on for a gauge and see just what pressure is actually there .
Try this company. Lots of cool things, but this setup might work for you
I’m curious why the only differences between the drum and disc 67 distribution blocks appears to be fitting port size? Are there internal differences not mentioned? What if, any issue, would there be using a 67 drum brake distribution block on a 67 disc brake car?
I believe it has to do w/ the lines. Fitting at the block end was different (can’t recall for a fact, but I thought the disc was bigger. Both are basically the same internally, as the “valve” was located in the rear of the car in 67- 68 they moved it just under the dist block
That’s what I’m thinking, just different fitting sizes on the line ends but I’m curious why Ford bothered? I mean to have a specific block with different ports just for Disc/Drum cars doesn’t seem cost effective especially when all they did was retrofit disc brakes onto the drum brake setup.
What if, any issue, would there be using a 67 drum brake distribution block on a 67 disc brake car?
I don’t see any issues as long as you have a prop. valve somewhere in the rear line.
My 1970 came with four drum brakes. I put discs on the front many years ago.
I’ve been all over this car for the last forty years but I don’t remember seeing any “valve” near the floorboard at the rear axle. Maybe I missed it.
Brakes do work well, a little sensitive but I’m used to it. I’m getting into the shop manual now and I don’t want to hi jack this thread but - should there be another valve on my set up? Thx
67,68,69 were the only years the factory had the proportioning valve separate in the system. 67 had it near the back in the line to the rear drums. 68/69 moved it closer up front near the master cylinder.
In 70 they had a combination block or how most just called it “the proportioning valve” as it does the job of both distribution block (name is obvious) and proportioning of the hydraulic fluid to the rear drum and from disc system.
Note. drum/drum setups didn’t have proportioning valves.
If you went disc on all four corners the setup is technically the same pressure to do both so you are ok but you want the front discs to engage before the rears so perhaps an aftermarket PV in the rear line to allow fine tuning would help you.
Thx for that, it helps. Between proportioning valve/pressure differential valve/metering valve - it can get confusing.
It would be nice if the brakes weren’t so “touchy” but - sounds like a lot of detective work for not much gain.
I still suggest an aftermarket adjustable proportioning valve to dial in the rears but if you didn’t change out your master cylinder for one designed for 4 wheel disc brakes you should consider that as well. the stock disc/drum MC has a built in residual valve that wouldn’t work well for rear discs.
Thx. Disc conversion only on the front. Still have rear drums. So m/c should be ok yes?
Having a proper dual bowl Master cylinder for disc/drum is recommended. Most will have a residual pressure valve integrated into the rear brake circuit for the drum brakes.
Residual valves are used to maintain constant pressure on the brake system, in this case the rear. For drum brakes, a 10 lb. residual valve is used to hold pressure against the springs in the drum. This allows the drum brake to engage more quickly and reduces pedal travel.
Good stuff. Thx.
How do I know if my m/c is correct for disc/drum front/rear?
I can only suggest seeing if there is a casting or part number. Was it part of a kit?
That was a long time ago. If there is a casting, I’m sure it’s in a super accessible place to see! 
I will look around. Thx
Permit me to up this thread.
I have a brake idiot light that stays on… I come to realize reading you guys that it might have something to do with this distribution block, however I still have brakes though the pedal is very very soft. might need to check that.
Also, I can see some fluid underneath the brake booster, might need to change both this and the master cylinder ?
