proportioning valve

[Bog Dog]

just recently did a power brake swap, is there a difference in proportioning valves on a non power brake and a power brake? the first part of the pedal you can feel the assist but to really get it stopped you have to hammer down on the pedal and it feels like there is no power assist. the unit was bought as a combo, booster and cyl.

 

[Torxhead]

I think if you are still using the oem prop valve it would be a good idea to change it anyway. I recently replaced mine and did notice a difference with power brakes and having power brakes prior. The big box 4wd outfits will have it and I was not able to get one at auto parts stores or brakes shops.

 

[BusaDave9]

It doesn't matter if you have power or manual brakes. But the jeeps that have front disk brakes have a different proportioning valve that jeeps that have drums all around.
Keep in mind that the master cylinder is what gives the front more pressure. The proportioning valve has to match the master cylinder. The proportioning valve CAN NOT give more pressure to the front or the rear. A proportioning valve can only reduce pressure on one line (front or rear). And even then only up to a point. Once the spring loaded valve is all the way one way full pressure is applied. So the proportioning valve can never INCREASE pressure to a failing brake system.

Check out this link:
Proportioning Valves - Proportioning Valve

A Proportioning Valve is installed in the rear brake line and allows you to adjust the rate of pressure rise to the back brakes. With an adjustable proportioning valve, you can slow down the pressure rise that occurs when you apply the brakes. Under braking, most vehicles transfer more weight to the front wheels. When this happens, the rear wheels lose some weight and can lock up if the pressure is too great too quickly in the braking process. Eventually full pressure is applied to the rear brakes through the proportioning valve.

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[Deerejeep]

Might be helpful for you. I'm headed to power brakes too and replacing rear disc.

Brakes

 

[tarry99]

just recently did a power brake swap, is there a difference in proportioning valves on a non power brake and a power brake? the first part of the pedal you can feel the assist but to really get it stopped you have to hammer down on the pedal and it feels like there is no power assist. the unit was bought as a combo, booster and cyl.

As mentioned before good brake systems are built and are not just thrown together..........Like Dave mentioned the Proportioning valve with the residual valves built in are setup for the particular system..........be it drum/drum , disc/drum Etc. Like wise the master cylinder has to be of the correct bore size and type to support the Disc's and Drums.

I would check your Vacuum at the Booster ...........you need about 20 inches of vacuum there for the system to work properly. Is your booster new or used? Is it a dual or single chamber? Are there any leaks from the source to the booster?
Sounds like you have enough stored vacuum upon the initial application and then it fades away.

 

[Bog Dog]

well a lot of good info. all the vacuum is good. the kit I got came with an adjustable proportioning valve for the rear, I was going to avoid putting it on but I think nows a good time. for installation on the valve, do you just run the rear lines through it and bypass the oem? I will give this a go and see what happens, if nothing gets accomplished then the power brakes can suck it and will go back with manual.

Jeep CJ 7" Disc Brake Booster Master Cylinder w Adjustable Valve | eBay this is the link to the set up I have if anyone is interested.

I don't think I mentioned it but the front are working well, maybe to well. when I said have to hammer down, that's what its taking to get the rear to work. like a big pressure difference from front to rear. all brakes and hardware are new, properly installed, adj, and blead.