Proportioning Valve?

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J

jar84203

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I have a 71 Duster that has been converted to 73 front disc brakes. My question is should a proportioning valve be installed to get proper brake pressures to the front and rear? From the looks of it, the previous owner never did. All I found was the brake light warning switch that illuminates the dash light if there is low brake pressure in one of the systems. Thanks in advance.
 
Is that switch in a brass block with the lines going to it?
 
Not sure if it's brass, but all lines go into it. It's mounted on the framerail just below the master.
 
That is your prop valve so you should be ok then. Let me see if I can find a pic for you
 
I was told, when I swapped 73+ disks into my Dart, that I should grab the proportioning valve from the 73+ as well.
 
Yea I just re read your original post I would find out what 1967dartgt is saying to make sure it's done right.
 
Yeah a pic would be great that way I know what I'm looking for at the swap meets.
 
The brass block is really a distribution block. The proportioning is done with wheel cylinder / caliper piston sizing. When I do a conversion I use the distribution block from the disc car just because I have it but one time used the drum distribution block to see and the brakes worked fine and the braking bias seemed "normal".

Proportioning valves actually limit pressure to the back brakes to keep the bias towards the front. When you get your conversion done take it out and do a hard stop. If the back brakes lock up before the front then you will need a proportioning valve.

I really wonder if they are indeed the same. If someone had an old parts book they could see if they were the same part number.


Chuck
 
this is what 340mopar is referring to

DSCF1838_Medium_.jpg
 
Mine is vertical and a little different. I'll try what 340mopar suggests and add a proportion valve if needed. Thanks
 
If you have just the distribution block for drum brake cars, add an adjustable proportioning valve to the rear brakes and adjust as needed.
 
340mopar said:
The brass block is really a distribution block. The proportioning is done with wheel cylinder / caliper piston sizing.
Click to expand...

The brass block, or Tee (as it is called in the Parts Manual) is fitted with valves as installed in the A-body. In addition, it contains the switch the activates the BRAKE warning light on the dash.

From looking at the parts manual, the rear wheel cylinder size is a function of the diameter of the drum. The 9" brake used one size piston, 10" & 11" brakes use another. There is no difference whether the car had disk or drum front brakes. Also, there is no difference in the front caliper piston size as relates to the drum size fitted at the rear.

340mopar said:
I really wonder if they are indeed the same. If someone had an old parts book they could see if they were the same part number.
Click to expand...

No. For the A-body, the parts numbers are 3420 021 for the drums, 3549 947 for discs in the 72 manual.
 
I was wondering what is the right size adapter for the front brake line of the proportioning valve? The proportioning valve on the top there is a tube sticking up and I can't get the right fitting to push it down. I bought a couple of lines but it didn't fit to screw on. the car is still using the original proportion valve. I was just wondering :)
 
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