proportioning valve (to be or not be)?

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I have all 4 tires the same size, 225s. Works fine. Don't forget, the rear brakes normally are much smaller than the fronts. Maybe that's why it works O.K.?
 
AJ/FormS said:
Hang on I didn't see anybody post their tire sizes.

And a final FYI, on the street, rear discs are a luxury; the drums are perfectly adequate, even for staggered-size tires.
The only advantage rear discs offer is freedom or near freedom, from fade, and quick pad changes. But as a streeter,when and where, are you gonna need to take advantage of these features.
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A/J have you ever drove a modern performance car with 4 wheel disk brakes?
The rear disks make a huge improvement in stopping power, my new Challenger R/T has completely spoiled me.
I also had the same mentality that drum brakes were fine on the rear until I bought that car.
 
67Dart273 said:
If you read the shop manual........and I've posted this till I'm blue....

Go to MyMopar they have them free.......they show you in there HOW TO REMOVE the residual valves out of a drum master. This is to overhaul the master

On my 67, which has 73/ 74 A body disc up front, and Lincoln Versailles in the rear, NO prop valve was needed, and furthermore, in my case, the STOCK 67 MASTER worked fine, gave me good pedal (manual master)
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question did you use the factory distribution block
 
I bought several new adj prop valves for ~$30 on ebay. I recall one was branded "Jegs", but all look from the same Chinese factory. Ideally, the fronts should skid just before the rears, tested in a wet parking lot. That is true regardless of drum/drum, disk/drum, or disk/disk. One could design any of these to work w/o a prop valve if you select the ideal bore calipers and wheel cylinders. But, that would also require many lab tests. So, an adj valve is best. The ideal setting also varies w/ tire changes and even weight distribution. Many trucks and vans (even minivans) have a proportioning valve which varies w/ the rear load. They have a lever which moves as the rear cabin sinks under load.
 
AJ/FormS said:
Hang on I didn't see anybody post their tire sizes.

The P valve is in there to prevent pre-mature rear wheel lock up..... period.
The factory put four same size skinny tires on these cars, and if the rear tires were to lock up, the rear of the car usually steps out to the side, and if you are asleep, then a spin is eminent ! You kindof want to prevent that.
Most of us hotrodders run big and little tire combos; with 225 to 245s up front and 275s to 295s out back. So for us the P valve is unnecessary, we can easily achieve correct proportioning with wheel cylinder size.
However rear discs may have more power to stop than drums. And then around she might go.
So
If you have staggered tire sizes as above, then you PROBABLY don't need any proportioning. And you for sure don't want any residual valves on your car AT ALL.

If you already have a P valve installed, just leave it on there it can't do any harm. But you may, MAY, not have optimum rear braking with it in the circuit. In any case it is easy to disable it at a later date.
Or you could install an adjustable valve, and defeat the oem one.

In every case, you will have to do some testing after everything is installed, to make sure the car stops straight. Chose your test location with care.

And a final FYI, on the street, rear discs are a luxury; the drums are perfectly adequate, even for staggered-size tires.
The only advantage rear discs offer is freedom or near freedom, from fade, and quick pad changes. But as a streeter,when and where, are you gonna need to take advantage of these features.
Click to expand...
Most of us run bigger tires in the rear anyway. I have 4 wheel discs, the stock proportioning block, 1987 dodge diplomat alum. master cyl, and have never even come close to locking the rear brakes.
 
I think to get the best possible braking you would want the adjustable PP valve, I would worry without the valve you would be leaving some stopping power on the table by either not enough or to much going to the rear.
 
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