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Home » Public Forums » GMCnet » Problem with brass body proportioning valve (Read about it in Winter 2021 Vintage RVing)
[GMCnet] Re: Problem with brass body proportioning valve [message #367162 is a reply to message #367161] Mon, 11 October 2021 14:43 Go to previous messageGo to previous message
stu@97381.com, Emery  is currently offline  stu@97381.com, Emery   United States
Messages: 232
Registered: June 2020
Karma:
Senior Member
That looks like the valve that I put on years back. I checked mine out some time back and it didn’t need a modification.
I don’t think that you could lock up the fronts before the rears if you had the modification or not.
If I were you I would not do anything to it. If your brakes are working now I would not mess with the valve.

By the way it really isn’t a proportioning valve. It should be properly called a combination valve. It puts a small amount of pressure on the front brakes before it puts the full pressure to both the front and read. It does not proportion any pressure to either the front or rears.
It also has a shuttle inside it which will turn on a light on the dash telling you if there is no pressure on either the front or rear. This is to tell you that you might have a leak in the system or low fluid on the front or rear.

Emery Stora
emerystora@mac.com



> On Oct 11, 2021, at 12:14 PM, Russell Keith wrote:
>
> So, is this the wrong combination valve?, Which I installed a few years ago. I see the PV2 / 12M86 part number. If I do the modification, am I more
> likely to flat-spot the rears before the fronts lock up? The brakes "appear" to be fine now, but perhaps I don't know any better. :roll:
>
> http://www.gmcmhphotos.com/photos/data/7010/medium/Combination_Valve2.jpg
>
>
> --
> Russell Keith,
> 1978 E2 "Harry" 403 (still carbureted), Danny Dunn Tranny, Thorley, Stock Brakes w/Remote Vacuum Brake Booster, Quad Bags, Dakota Digital Dash, 6.5 kW
> Onan, Dunedin, Florida
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> GMCnet mailing list
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