Proportioning valve question

-
jawbone

jawbone

Cuda_queer
FABO Gold Member
Joined
Mar 17, 2017
Messages
644
Reaction score
301
Location
Richardson, TX
I'm going to try to keep this simple and at the same time hopefully obtain a simple answer. I have a 68 Barracuda /6 with 9 in drums. Motor is out. New motor is waiting on clutch at the moment before it goes in. Observed the distribution block on frame rail and wondered if, while engine was out, I could install proportioning valve. Brake wise, my intent is to use Mopar front disk and rear drum. This leads me to the question; is there a replacement proportioning valve that fits the same place on frame rail and what do you guys do for brake lines between new master cylinder and valve? Bend to fit or is there a supplier out there for just such a change. I'm going to guess that none of the lines fit; even the brake lines to the valve. Thanks.

20231007_125506[1].jpg
 
up to some year the disk / drum proportioning valve was a separate valve mounted to the rear (6 inches or so) of the distro block in the rear line.

there is a later year ( 73???) distro / proportioning valve combo that might bolt into the same location as your distro valve with only minor movement of your tubes.

If it was me I would opt for year specific parts, less issues down the road.
 
Dana67Dart said:
up to some year the disk / drum proportioning valve was a separate valve mounted to the rear (6 inches or so) of the distro block in the rear line.

there is a later year ( 73???) distro / proportioning valve combo that might bolt into the same location as your distro valve with only minor movement of your tubes.

If it was me I would opt for year specific parts, less issues down the road.
Click to expand...
Thanks for the reply Dana67Dart. Point to stay with year specific parts is well taken. Have made an effort to do just that but availability of parts and lets not forget my misunderstanding of options has led me astray at times. Sometimes I just do nothing. Have contemplated this brake issue for quite some time. I could go larger drum/drum without issue.

Am I to understand correctly a smaller rear wheel cylinder will compensate as well? That's not stepping too far out of bounds. I am also very reluctant to purchase non Mopar disk brakes. What happens if I need replacement parts down the road. I have already forgotten what year front calipers I have. Think they are 73 or 75. The Kelsey Hays option sounds great if I want to stick with 4 inch bolt pattern and skinny tires. That was my original plan. Have all the makings for rear drums 10 x 1.75. Probably more money to flush.
 
jawbone said:
Am I to understand correctly a smaller rear wheel cylinder will compensate as well
Click to expand...
You can do that and through experimentation maybe come up with a combo that stops better than stock.

Or...

You can use the decades of engineering that went into the factory setup.


If you go 73 up single piston large built pattern then the 73 up master and 73 up combo valve would be the way to go

If staying sbp I would go with KH and related parts.
 
Dana67Dart said:
You can do that and through experimentation maybe come up with a combo that stops better than stock.

Or...

You can use the decades of engineering that went into the factory setup.


If you go 73 up single piston large built pattern then the 73 up master and 73 up combo valve would be the way to go

If staying sbp I would go with KH and related parts.
Click to expand...
RMS may be the deciding factor. Think the axles are not selectable. In fact they may require disk brakes. If so then I wasted more of my time.
I do like your prospective. It's just two choices.
 
Let me make a suggestion. About 15 years ago, I installed a front disk brake kit in my 69 Barracuda. It came with an adjustable proportioning valve. It has a knob on the bottom that could be turned to vary front to rear pressure ratio. It works really well. As I remember, the brake lines fit pretty well. You could install one of those now. If you switch to disk brakes, you'll need a proportioning valve anyway.
 
Last edited:
harrisonm said:
Let me make a suggestion. About 15 years ago, I installed a front disk brake kit in my 69 Barracuda. It came with an adjustable proportioning valve. It has a knob on the bottom that could be turned to vary front to rear pressure ratio. It works really well. As I remember, the brake lines fit pretty well. You could install one of those now. If you switch to disk brakes, you'll need a proportioning valve anyway.
Click to expand...
That's the idea initially due to my accessibility to dist. valve. Swap it out for the combo proportioning valve as shown by Dana67Dart. I'm trying not to perform flaring procedure while under the car which I assume necessary to install non integrated proportioning valve.
 
jawbone said:
I'm trying not to perform flaring procedure while under the car which I assume necessary to install non integrated proportioning valve.
Click to expand...
Inline tube does sell the two lines needed to make the earlier separate version up.
 
Dana67Dart said:
Inline tube does sell the two lines needed to make the earlier separate version up.
Click to expand...
Very good to know. Thanks for the update. Will contact them Monday and get the ball rolling. Many thanks from everyone for their comments.
 
Don't forget you can also simply add an aftermarket and or adjustable valve in series with the rear tube
 
Something to know about Inline Tube proportioning valves is you must replace the copper sealing washer with a new one as the Inline original copper washers are not pliable enough to seal and will leak no matter how much torque you put on them. But once you replace that copper washer you are good to go, no other issue with them. But that copper washer is a pita to replace after it’s all installed with headers nearby…
 
Wvbuzzmaster said:
Something to know about Inline Tube proportioning valves is you must replace the copper sealing washer with a new one as the Inline original copper washers are not pliable enough to seal and will leak no matter how much torque you put on them. But once you replace that copper washer you are good to go, no other issue with them. But that copper washer is a pita to replace after it’s all installed with headers nearby…
Click to expand...
Boy that can ruin a day. Thanks for the heads up.
 
Inline Tube tech support was of no help other than securing the information that a proportioning valve is the same as a hold off valve and that BLK250 was a combination of each. MD2274 does not exist in their system.
 
Hold off vs proportioning are kind of the same.

Technically hold off is a delay then full pressure to front and back.

Proportioning is 500psi in 100 psi out (made up numbers)

Each MIGHT have the other as part of its circuitry
 
Dana67Dart said:
Hold off vs proportioning are kind of the same.

Technically hold off is a delay then full pressure to front and back.

Proportioning is 500psi in 100 psi out (made up numbers)

Each MIGHT have the other as part of its circuitry
Click to expand...
Thanks for clearing that up. Just more confusion. I'm getting to know it well but that's what makes this fun. I'm learning.
 
If you look in the Factory Service Manual for the year your are replicating there will be a description of what the valve does.


Also don't be shy about buying used valves. As long as they are not gummed up inside or the o rings etc dried out. They will work
 
Dana67Dart said:
If you look in the Factory Service Manual for the year your are replicating there will be a description of what the valve does.


Also don't be shy about buying used valves. As long as they are not gummed up inside or the o rings etc dried out. They will work
Click to expand...
Did they even use holdoff valves on cars of 68 era? I ask this because i never have heard of one. Will check my manual. Thanks for the suggestion.
 
This is from 67 FSM ( the proportion is close to 65%)

Screenshot_20231010-121951.png


69 FSM ( the proportion is closer to 75 %)
Screenshot_20231010-122649.png



73 the combo valve has the same spec as the pre 73 separate valves but the combo "metering" valve is a bit different in function

Though I don't think they were used on A bodies.

Screenshot_20231010-123154.png
 
Dana67Dart said:
This is from 67 FSM ( the proportion is close to 65%)

View attachment 1716152290

69 FSM ( the proportion is closer to 75 %)
View attachment 1716152291


73 the combo valve has the same spec as the pre 73 separate valves but the combo "metering" valve is a bit different in function

Though I don't think they were used on A bodies.

View attachment 1716152294
Click to expand...
I'm impressed with your knowledge and ability to produce the documentation on such short notice. It's exactly as you indicated. Thanks for the lesson. Just to let you know how uninformed many people are. Was talking to gentlemen at Accurate Exhaust today. He said distribution block was a proportioning valve due to presence of dual master cylinder. Best he stick with exhaust.
 
You must log in or register to reply here.
-

Back
Top