GM Brake prop valve piston which way ?

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Tom68
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GM Brake prop valve piston which way ?

Post by Tom68 »

I have two, they were assembled one each way.
I have two pics off the net, same thing.
It does matter, there's a piston in the piston.
I'm too lazy to work out how it works to then decide.
master_prop.jpg
StatesmanPropValve.jpg
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Rick!
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Re: GM Brake prop valve piston which way ?

Post by Rick! »

The bottom pic in your post shows the valve/shuttle pointing backwards as the pintle sticks out the end of the valve body.
One cutaway
cutaway diagram
two more cutaway versions
62-67 Nova cutaway

If you use google, insert "before:2023" and then type in your search, you can get a lot of images of proportioning valves. I used "before:2023 GM brake proportioning valve cutaway" and came up with the cutaways and diagrams.

In the big picture, if the barrel with the o-ring is backwards, you'll either get premature rear brake lockup or the brake light will come on during bleeding and never go off (if the ignition is on), requiring a reset and reassembly with the o-ring barrel position reversed.
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Tom68
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Re: GM Brake prop valve piston which way ?

Post by Tom68 »

Cheers, looks like this is an Aussie only version, quite a bit different to the US one.
Ignorance leads to confidence more often than knowledge does.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
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