proportion valve or distribution block

[easyrider]

I put power brakes on my truck and it came with a proportion valve which I included with the installation. 4 wheel drums...I'm having trouble getting brakes and the light on dash won't go off. I've been told that my 68 didn't come with a proportion valve and I'm not even sure about it coming with p/b. So, I was told that what I needed was a distribution block instead, but when I tried to find one to purchase, no one knows what I'm talking about. I was going to put disc brakes on front, but because of the pandemic, no one has the parts I need and no one knows when parts will be available. So, I decided to stay with the drums all around until parts become available. If I can't find a distribution block to connect line from wheels to m/c can I just bypass the block and just run lines straight from wheels to m/c?? I'm going around in circles and am not accomplishing anything. I need to get brakes, so help me figure out what is the best way to connect m/c to wheel lines. Any and all information will be appreciated. Thanks....

[jimijam00]

Call Pirate Jacks and they will hook you up with what you need.

http://67-72chevytrucks.com/vboard/s...d.php?t=790788

[gmc684x4]

Here is a picture of the distribution block on my 68 K10 chassis should be the same for a rwd chassis I can not compare as both my rwd drum trucks have no master setup
You can see the brake light wire hanging down doyou have a block like this ?


I included a pick of my 72 c10 (blue firewall) to show the difference looks the same as my 72k10 expect where my dad added a line lock on the rear

The Distribution block will be the same power or manual brakes


The master cylinder will be different on power brakes vs manual brakes

You could look and ask on the parts board if they have one for sale

As for disc brake upgrades all depends on how you look for parts is your truck a c10 ? I have read you can use 73 87 spindles with appropriate ball joints 73 87 outer tie rods and 77 elcamino inner rods and use your center link
I have not confirmed this as i have a 72 suspension to use

One thing about 73 80 there was a light brake option available to them as well

this fact is a good read through on most options for a disc brake upgrade

http://67-72chevytrucks.com/vboard/s...d.php?t=456889

[easyrider]

Here is the photo of mine. is this a proportion valve or a distribution block?

[gmc684x4]

its a distribution block

https://www.inlinetube.com/products/pr112

[jocko]

Originally Posted by easyrider

I'm having trouble getting brakes and the light on dash won't go off.

Can you elaborate on "trouble getting brakes"? No front, no rear, none at all?

Can you elaborate on the proportioning valve you mentioned your truck came with? Is it from a later year chev, as in a a combo valve, or is it aftermarket? If the latter, is it adjustable? (pics please )

By the way, there's nothing "wrong" with having a proportioning valve rather than a distrib block on a drum/drum system, your brakes should work fine - but the bias may need to be adjusted a little bit if it's designed/preset for a disk/drum setup - that is why most, not all, aftermarket proportioning valves are adjustable. It IS possible the proportioning valve is bad - but did your brakes work fine before you installed the booster? Was the same proportioning valve on before you installed the booster? If you do plan to eventually install front disks, you would then not want a distribution block - so based on what it sounds like your plans are, it might be better to find the root cause of your problem first - you may need nothing at all at this point in time. If you just want to stay drums, then what gmc684x4 posted is what you need!

Anyway, your problem may have nothing to do with your proportioning valve, but you never know, a description of what is happening would help folks help you with the diagnosis. Got any pics of what you have right now?

Regarding the brake light - is the dash brake light wire connected to your new proportioning valve? (I assume so, just gotta ask). Assuming the answer is yes, who is the brake kit mfgr, or was it a kit at all, i.e. do you just add a stock 68 booster setup? If a kit or aftermarket proportioning valve mfgr, have you called them to ask how to reset the shuttle valve in it? Some of the aftermarket ones may need to be reset in a way that is different from the originals.

EDIT: also note that if you swap in front disks eventually, the front brake line system should technically be 3/16" vice the drum system's 1/4". Lots of folks will tell you they don't swap lines, and that is fine - the system will still work, but it's not how the disk brake system was originally designed - just something to be aware of.

[gmc684x4]

Jocko his pic has the engine behind it its a stock distribution block with the brake light wire removed from it

My question did you change the master cylinder when you added brake booster manual master cylinder will not work with a power booster the rod hole is deeper and the power booster will not push it far enough to to apply pressure to brakes

Stock booster or aftermarket ?

A miss match won't let you fully bleed your brakes you might still have air in your lines as well keeping the brake warning light on

[HO455]

That is the standard drum brake distribution block. It allows the brake lines to be easily brought together and it also contains the switch for the brake failure light. The switch is a moving cylinder in the bore that is normally in a centered position. It will stay in that position as long as the brake pressure in the front and rear brakes is equal. If pressure is lost in one side of the brake system then the cylinder will slide in the bore causing the brake light to come on. To correct this the cylinder must be forced to return to the center position once the problem has been repaired.
A portioning valve will delay or reduce the amount of braking power to the rear brakes. They became necessary when disk brakes were installed as it takes a larger volume of fluid to move to make a disk brake operate. That means in a disk/drum system the rear brakes will apply before the front brakes do. Not the safest condition. To prevent this condition a mechanical device delays the pressure being applied to the drum brakes. Early systems had a separate device for this but by the 1970,s GM had engineered the delay device into the distribution block and now they were referred to as a proportioning valve. Hence the confusion.

[jocko]

Originally Posted by gmc684x4

Jocko his pic has the engine behind it its a stock distribution block with the brake light wire removed from it

DUH! Thanks for pointing that out, I thought you had posted 4 pictures, missed his added post.

And excellent point on the depth of the pushrod hole on the manual vs power mc. That could easily be the problem.
I guess the first question would be whether the intermediate pushrod was even installed (i.e. between booster and mc) - because the original manual system of course doesn't have an intermediate push rod.

Interested to see where this diagnosis goes

[jocko]

Pic 1 is of a MANUAL brake master cylinder - it does NOT work with a booster (even though it's pictured next to a booster). And the 2nd pic shows the short intermediate rod poking out the front of the booster when it is fully seated for reference. 3rd pic shows the overall size of that push rod (it just pulls out, it is not retained in the booster). Hope these help, forgot I even had these pics from a 66 brake job I did once - where I learned all this the hard way.. ha. The "answer" to my obvious problem of having a manual brake mc and wanting to add a booster was to a) skip the booster and just convert to the dual res mc (which is why I was doing the upgrade in the first place), or b) return the mc and buy a power brake mc. (I opted for "a" in my case, but was getting ready to sell, had I been keeping it, I'd gone with option "b"). A power brake master cylinder would have a much, much shallower hole in the rear of the piston of the master cylinder than what is shown in pic #1. You can image how shallow when you see how little the push rod sticks out of the booster in pic #2. It really is a very shallow bore, I'd say <1/4" or so, but obviously shallow when you look at it from the same view angle as Pic #1.

EDIT: Added Pic #4 - this is what the shallow hole of a power brake mc looks like.

[easyrider]

I purchased this set up from one of our members who was going to disc brakes. I got m/c, booster, valve, bracketry as a unit that came off his truck. I don't know if stock or after market, but it had been on his truck for a year before he converted, so I assume it all was fine. The rod to booster also was a part of package. I took my non power brake unit off and installed all of this at same time. All in wheels are new from shoes to brake cylinders to new lines. I feel like it is an bleeding air issue, but we bled it all more than once and no better. I can put on brakes and it will slow down back wheels turning but not stop (rear on jack stands). I guess I should start with m/c and bleed, then attach valve and bleed from there then work my way through wheels. I just feel I am going around in circles and missing something each time.

[easyrider]

Here are photos of back of m/c and the rod coming out of the booster. Can you tell me from the photos what exactly I have???

[easyrider]

here is another shot

[jocko]

It "looks" like you have a deep hole in the mc piston (indicative of a manual brake mc), however, the intermediate rod coming out of the booster is also long (which I haven't seen before...) (makes me wonder if in 67-68, maybe even thru 70, the power and non-power mc's were identical... hmm (i.e. all drum/drum systems). 71-72 power/manual mc's are not interchangeable, for example). If the member you bought this whole combo from said it was working and you've not changed anything, it "should" work based on the pictures above. One thing to check: I'd measure from the full depth of the mc piston hole to the mating surface of the mc - and then compare that with the measurement of the mating surface on the booster to the tip of the pushrod. The 2nd measurement should only be a "hair" shorter than the 1st. In other words, as long as the pushrod isn't engaging the mc piston when assembled - and as long as there is very little slop in between the tip of the push rod and the inner depth of the mc piston, you should be good. Also note that your push rood appears to be adjustable. I think there is nothing wrong with your arrangement, it should work - assuming the measurements make sense once you compare them. Is the pushrod fully seated in the booster in your first picture? (I assume yes). With all the info you've provided, seems more like a bleeding problem only at this point. You mentioned the brakes kinda work - do they feel "boosted" like power brakes should feel when you depress the pedal (even if braking perf is poor) - or do they feel the same as when you had just manual brakes before (but with poor perf)? Thanks for all the pics and sorry I missed the first set - they are helpful. One note on the bleeding process - you mentioned bleeding the mc, then at the block, then at the wheels. There should be no need to bleed anything at the distrib block, just mc bench bleed and then the wheel cylinders. I normally have an assistant do the pedal pushin, but many members have had success with gravity bleeding the brakes, might be worth a google on the site.

[easyrider]

Thanks to all of you assisting me in working out this problem. I'll bleed the m/c and then at the wheels again and see what happens. I'll be letting you know how things go from here..and, again, thanks....

[j_cst_10]

I have done a few custom brake set ups. By custom I mean using different master cylinders than stock, rear discs, upgraded front calipers that were stock on different GM vehicles, etc.

In order to take ALL the guess work out of what you are doing I would run the fronts to a brass T and the rears to an adjustable proportioning valve. Then you won't be questioning if pieces/parts are correct.

If you are running drum rears you can plumb in a residual pressure valve if needed.

If you want to retain the brake warning light, I think wilwood makes essentially an adjustable combination valve that does all the same things as I described above but in a one piece package, i.e. full pressure to fronts, adjustable rear with warning light.

I have wasted big $$ in brake fluid trying to get brakes right. If you decide to go different than a stock set up take the guess work out of it.

[LNP]

I switched my 69 from manual drum brakes to power disc/drum and this is the valve I use. https://www.summitracing.com/parts/clp-pv-2


Someone might have answered this and I missed it but No you can not safely directly attach the brake lines from the wheels to the master cylinder. The valve will insure even brake pressure for safe and controlled braking.

[70STOVEBOLT]

You should be able to use the manual master cylinder with that Bendix booster, but you will need the correct pedal pushrod, the manual one will not work.

[LNP]

Originally Posted by easyrider

I purchased this set up from one of our members who was going to disc brakes. I got m/c, booster, valve, bracketry as a unit that came off his truck. I don't know if stock or after market, but it had been on his truck for a year before he converted, so I assume it all was fine. The rod to booster also was a part of package. I took my non power brake unit off and installed all of this at same time. All in wheels are new from shoes to brake cylinders to new lines. I feel like it is an bleeding air issue, but we bled it all more than once and no better. I can put on brakes and it will slow down back wheels turning but not stop (rear on jack stands). I guess I should start with m/c and bleed, then attach valve and bleed from there then work my way through wheels. I just feel I am going around in circles and missing something each time.

There is a possibility the master cylinder itself has an issue. Did you try bench bleeding the master cylinder before installing it? Sometimes any angle at all will keep it from bleeding out completely. Try putting it in a vice level and then bleed it out. Then after reinstalling it rebleed the rear brakes to see if that helps. Make sure while bleeding the master cylinder never goes low on fluid as it can easily suck in air and ruin the work you just did.