Proportioning valve?

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chodge

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I am new to the website. I am working on a 67 valiant. I have heard that for cars under 3000 lbs you dont need a proportioning valve. Has any anybody put disk brakes on the front with without a porportioning valve?
 
Vehicle weight has nothing to do with it. Disc brakes take more line pressure to work than drums. If anything, you would be more likely to have the rears lock on a light car than a heavier one.
Plenty of people add discs without changing to a prop valve, but it's really not a good idea.
 
Yes I have no p-valve. But I have 295/50-15s out back and small wheelcylinders. It is possible to balance the system without one. I bought an adjustable one expecting to have to use it, but never required it.
 
finelines.com sells them new. IF your doing 4 wheel disc they claim you don't need 1. Let's see that Valiant :)
 
73 and up A-bodies don't even use them. I let Chrysler design the last system on the car I converted. I just used everything front to rear from a 75 Dart.
 
mcodecuda said:
73 and up A-bodies don't even use them. I let Chrysler design the last system on the car I converted. I just used everything front to rear from a 75 Dart.
Click to expand...

Seriously? This cant be right. both the 74 and the 2 75 darts I have owned had proportioning valves, or are you saying they were only junction blocks? I have a hard time believing there was no proportioning valve in 73 and up A bodies...
 
Drum brake systems are balanced with shoe size and wheel cylinder diameter. Four wheel discs are balanced the same way...but disc/drum are always fed through a valve. It'll lock the rears anytime you got aggressive with the brakes otherwise. Contrary to popular myth, drum brakes grab harder than discs. The disc brake's only advantage is in repeated stopping and a better ability to dissipate heat from higher speeds.
 
Many years ago, our fist 67 fish, was a slant 6 car. Small drums all around.
Front disc brakes from a 73 Duster went under it first. Later a large bolt pattern 7.25 ( today I cant remember where I got that rear end as if it matters LOL ) for LBP on all 4 corners. Never did upgrade the OEM drum brake master or install a proportion valve.
It would lock and slide all 4 in a panic stop but it did stop.
 
AJ/FormS said:
Yes I have no p-valve. But I have 295/50-15s out back and small wheelcylinders. It is possible to balance the system without one. I bought an adjustable one expecting to have to use it, but never required it.
Click to expand...
I also did a disc brake up grade on my 73 Duster. I installed a pv, but it's set at wide open as my 295 / 50- 15's never lock up either.
 
AJ/FormS said:
Yes I have no p-valve. But I have 295/50-15s out back and small wheelcylinders. It is possible to balance the system without one. I bought an adjustable one expecting to have to use it, but never required it.
Click to expand...
This is the BEST way to do it: vary rear wheel cylinders or vary the pad & shoe materials. Using a prop valve of any type with a spring loaded piston (that doesn't self-adjust with brake pedal force) to bleed off pressure always is a compromise at some point as brake pedal force is varied. (But this is more than most folks want to deal with.)
 
A '73 and newer disc brake equipped Mopar came with a 1 piece combination valve. It included metering (hold off), as well as proportioning.
 
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