4 wheel drums are proportioned

[ICEMAN6166]

got into this discussion yesterday while rebuilding my plow frame and talking about the line lock i traded for.

i learned something new or at least was given a perspective that i had not previously considered about brake proportioning

when converting to a dual master cylinder it is necessary to have either the factory juction block used with the dual mc on the frame or an adjustable proportioning valve as the factory block does have a proportioner in it to give the front brakes more stopping % than the rear.

the idea of using a dual mc and running one side directly to the rear and the other to a tee to the 2 front lines results in equal pressure to both front and rear brakes and is incorrect and should not be done as the frame block/proportioner is part of the improvement of the dual mc system and is designed to give the front brakes the added percentage over the rear. your brakes will still work but you are not getting the full effect of the upgrade.
its just not a 5 way tee.

since i have always taken the blocks and used them in my dual conversions i have no worries as to my systems but i have read of some who did not.

[charliemccraney]

As I understand it, a proportioning valve reduces the pressure only under very sudden, hard stops like in a panic situation, to prevent the rear wheels from locking up. Under normal circumstances full pressure will go to all four brakes, which makes sense because you want to be able to remain stopped which may not be possible in some circumstances if all four brakes don't receive full pressure.

[slickmainer]

can those blocks be bought new from napa or are they only on parts trucks?

thinking dual master with 4way drums...both on the 66 and the 61

[R Pope]

The original setup didn't need a proportioning valve, what has changed? The single systems often had different size slave cylinders or brakes, end to end, to "compensate" for the different weights.
If you run all stock drums, you won't need a valve.

[ICEMAN6166]

the valve is in the 5 way block.
i had always thought it to be just a tee connector but was informed that is not the case.the person who gave me the information has far more mechanical experience than i do which to me is enough to take it as correct.

i do not know if you can buy them at napa or not having always taken the ones i used from 67-72 4 way drum equipped trucks.

when i do mc conversions i make them the same as the factory, i get the part used by ford and the correct mc for the trucks so far they have been all 4x4s so i get f250 4x4 4 wheel non power drum brake mc's. have not had any issues or problems and do not intend to change the way i do them.

my intent here was to inform of what i found out, i was certain i did the correct thing when i did my conversions and now i am absolutely convinced.

[tomsrod]

An interesting and timely topic for me. I recently completed, or so I thought, the dual master cylinder conversion for my drum/drum setup. I used a new power booster/master cylinder and power booster brackets from a 67. I ran one line to the rear brakes and another to a splitter for the two fronts. It works well and I like the new "feel". I never thought to look for the proportioning valve (or distribution block as some have called it) as I thought drum/drum did not need one.

I can find a 5 way connector at Napa, but it seems I will need to find a 5 way block from a 67-72 drum/drum and plumb it as it is on the donor truck. Does it matter if it is F100, F250, 4x2 or 4x4?

Pat

[Hawkrod]

I am very curious about this "source" as I have never found this to be a fact and I know for sure that the junction blocks are not proportioned until the much later. In fact, even in cars with disc brakes the junction blocks did not contain a proportioning valve until 1970 on a Ford. Prior to that it was just a junction block with a seperate proportioning valve. The Ford parts books and the Ford brake service manual show no proportioning blocks for that era so I am confused about what you were told. Ford adjusted brake values by sizing wheel cylinders and shoe/drum sizes and the junction blocks definitely did not contain any proportioning mechanism in the 1960's so if that is what you were told it is BS. hawkrod.

[64 f100]

Hawkrod, I have a lot of respect for your knowledge, but I know for a fact that Ford sold proportioning valves with 68 part numbers. I even know where there is a NOS one for a truck still in the box.

Rich

[ICEMAN6166]

i somehow had a feeling this would stir up the soup.
i will have a further discussion with the source on this, neither one of us is afraid of being wrong and can/will admit to it if it is the case.

the exploded diagram shows the block but does not show anything internally.


if i had an extra one i would cut it or otherwise examine and look inside.

[HiBoy63]

My understanding is that the distribution block is there on a drum drum setup so that if you loose front or back brake line or pressure you will still have either front or back brakes working. It is only a proportiong valve in later models when they went to disc up front and drum in the rear also disc front and disc rear. I pulled a mc with booster from a 73 f250 4x4 that was drum at all 4 corners. It has a distribution block but it looks a little different than a proportiong valve. There are some good vids on youtube on the subject.

[HiBoy63]

Brian thanks for that exploded diagram as the block looks to be the same one I obtained from the 73 drum drum 4wd that I got my mc and block from. This will help me figure out where to run my lines when I go to plum it in on the 65 this summer.

[tomsrod]

I found one today on a 67 F250 4x2 and it only cost $4. I looked a long time on the computer and did not find any new ones anywhere. In checking my parts book, Ford calls the 2B257 part a "Valve-Brake Pressure Differential". It probably is closer to a distribution block than a proportioning valve since it is not adjustable. It doesn't really matter what is called....it does what the above members pointed out.
From what I've read, in 1967 it was a government ordered safety device to alert the driver of pressure loss by a light on the dash as well as the safety of keeping pressure in one line if the other went bad. I'm going to use it since I have a 1967 dual master cylinder installed on my truck. I might even try to use the warning light feature.

[BigMike]

I just drag my feet Flintstone style

[64 f100]

Thanks for the clarification on the brake block/valve Ice. What I may have seen then would be the block you describe not a true proportioning valve. Next time I'm down there I will check on the valve. May just buy it to have for future use. The place also has two NOS front I-beams I may buy also. Guy is a little hard to deal with. Got some wierd left over parts from a dealership auction several years ago.

Rich

[TXSlick]

ICeman, I believe you are incorrect on that one. The drum brake trucks have a differential pressure valve in that distribution block that LOOKS sort of like the one that has the proportioning valve in it, but it does not. It is shaped like an "H" and does not have the proportioning valve.

On the disc brake valves, they are very similar but the part of the "H" going to the rear brake line is slightly offset and has a needle and seat in between the IN and OUT connection. The needle is spring loaded, and has to see x amount of pressure before it unseats and lets pressure to the rear brakes. The drum / drum valve does not have the offset and the spring loaded needle.

Both have the differential pressure valve, but the disc brake unit with the proportioning valve in it is different, and is properly called a combination valve, since it has both.

What most people do not realize, is converting to a dual piston master cylinder offeres no redundancy without the differential pressure valve in the system. Its function is to shut off flow to the brake lines if there is a leak. If the front has a leak, the pressure from the rear lines shift the valve to shut off flow to the front, leaving the mc something to "pressure up" against so you still have some braking. Same is true vice-versa if the rears get a leak. Without the diff pressure valve, ANY leak will take the master cylinder right to the floor. To verify this, just crack open one wheel cylinder using a tandem master cylinder and you can press the pedal right to the floor. With the diff pressure valve, it will go to the floor ONCE, then it will make pressure as the valve seals off the leaking part of the system.

All vehicles 1967 and newer have the differential pressure valve.

[charliemccraney]

Now that explains a lot. I've noticed that the pedal will go to the floor if either circuit is disabled (ie leaking) and wondered just how is that safer. Now I know, it's not. I don't recall any mention of a differential valve in any of the aftermarket kits I've looked at. I wonder if a universal one is available.

[Hawkrod]

Hawkrod, I have a lot of respect for your knowledge, but I know for a fact that Ford sold proportioning valves with 68 part numbers. I even know where there is a NOS one for a truck still in the box.

Rich

I am not sure what you are saying, I know for a fact that Ford sold a proportioning valve and installed it on all disc/drum trucks but it is not the distribution block that Ice is talking about on a drum/drum vehicle and shows in his picture. Your statement does not disagree with what I wrote at any level. The item *2263 shown in Ice's diagram is a pressure differential switch/junction block that lets the driver know when part of the brake system has failed by turning on a dash light and it is not a proportioning valve as has already been noted by TXSlick. Also note that the comment about "It probably is closer to a distribution block than a proportioning valve since it is not adjustable" is not accurate because a true proportioning valave does not need to be adjustable and the vast majority of them are not but on a 67 4X2 it would be a junction or distribution block not a proportioning valve. I think part of this misunderstanding is many people do not understand what a proportioning valve is. A proportioning valve is normally only installed in the rear brake circuit of a vehicle and is used to prevent rear lockup before front lockup. It is a pressure or gravity sensitive device that usually uses springs or gravity controlled balls to restrict fluid flow to the rear brakes under heavy braking. In a combination block (a later model junction block with the proportioning valve built in) the proportioning part is only through the line to teh rear brakes and has nothing to do with the front. 95% of the time a proportioning valve just sits on your vehicle doing absolutely nothing and to that point very few aftermarket ones are installed properly as you really need to test and adjust on a wet bed or it won't be right. Hawkrod