Wondering if anyone can help with info disc brake prop. valve.

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rtse66

rtse66

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Just bought a used Kelsey Hayes disc brake kit for a 65-72 a body and got the disc brake proportioning valve w/o lines in the pic. Sitting in my parts bucket is the valve with all the lines still attached. The only car I ever remember parting with disc brakes was a 70 satellite with factory single piston disc brakes. I know it's a b- body but does anyone have any info or experience with this.
71 duster valve has k/h 141-0 x, the other has k/h 155-0 x so both are Kelsey Hayes.

IMG_20230830_151922447.jpg
 
I used one from a 70 Duster on Vixen, however, it did not have that adapter on the top. The line from the master cylinder screwed right into the top of the valve. The ONLY mod I had to do was go up one size on the fitting going to the rear brakes. All I had to do was cut the old fitting off, get the correct fitting, slide it on and reflair the line and screw it on. Other than that, the whole thing was a bolt on swap, dual reservoir disc brake master cylinder and all. I still have not swapped on the discs yet and it stops great. I would use the one from the Duster.
 
The B-body combination valve includes a metering valve in the front line.
The A body combination valve without lines did not have a metering valve in the factroy system.
AFAIK the 'knee point' for both valves is the same, although the proportioning may be slightly different above the knee point.
The adjustable proportioning valve would be used with a distribution block (aka safety switch) that did not have the proportioning valve built in.

Look in the 1970 Hydraulic Brake booklet here for illustrations of the valves and what they do.

Master Technician Service Conference - Chrysler's Training for Mechanics

The Imperial Mailing List Online Car Club is dedicated to the preservation, appreciation and restoration of Imperials and Chrysler Imperials of all years, models and body-styles.
www.web.imperialclub.info

Also available in pdf format at www.mymopar.com -> Master Tech - > 1970
 
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^^THIS I was going to suggest looking up a few in the service manuals. There has been changes between body lines and years.

Run over to MyMopar.com and download a few service manuals, free. There are diagrams for at least part of them in there
 
I don't know what year those parts are from, but up through 1967 at least the proportioning valve was a separate object from the distribution block (safety switch) which you show in the photo (two different versions). It was plumbed into the rear brake line and located along the frame rail, and it doesn't look like the seller packaged it up for you. Too bad. So if you wanted to use the distribution block provided, you would need to plumb a PV into the rear brake line (this is actually dead easy — no cutting or flaring required — just attach the PV directly to the rear brake line and buy a short length of premade brake line to go between the PV and the distribution block — you can form it into a loop so it all lines up with the factory hard lines). I used a Summit adjustable PV for this application.

The other distribution block shown allegedly contains a proportioning valve (this is how Mopar did it on later models), but I found this created too much rear bias on my A-body, and it cannot be adjusted, so I went ahead and installed an adjustable PV as described above. BTW I had to crank it 75% "down" for proper balance.
 
The smaller device in your picture is a brake hold off valve, it goes on the front brakes on disc brake cars. I'm not sure what cars used it, my 69 C-Bodies have it, this setup uses the earlier style distribution valve.
2021-10-17_006.jpg



Alan
 
Cuda Al said:
The smaller device in your picture is a brake hold off valve, it goes on the front brakes on disc brake cars. I'm not sure what cars used it, my 69 C-Bodies have it, this setup uses the earlier style distribution valve.
View attachment 1716135613


Alan
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I've never seen one on an A body.
 
What I learned in the mid 80s going to school for automotive mechanics is that disc brake systems need to hold a small amount of residual pressure in the lines to keep the fluid from bleeding back. If I remember right is because there's a lot more volume in a disc system than drum. That might be what it's for.
 
rtse66 said:
What I learned in the mid 80s going to school for automotive mechanics is that disc brake systems need to hold a small amount of residual pressure in the lines to keep the fluid from bleeding back. If I remember right is because there's a lot more volume in a disc system than drum. That might be what it's for.
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Its the other way around. The residual valve is in the drum brake circuit because the springs apply pressure on the wheel cylinders.
The 'metering valve', aka 'hold off valve' is to slightly delay the front brakes so they don't lock up on initial application when braking on slick surfaces.
 
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