Mounting proportioning valve on frame questions

[crakarjax]

I'm redoing all my brakes and lines soon and want to mount the prop. valve on the frame. I've scrounged up all the info I could but didn't find the answers to these questions yet:

- Where is the best place to mount the valve? I read that the later years have it mounted on the frame behind the rad support, but that seems further forward than is necessary. I'm thinking of tucking it in the frame rail just rearward of the front crossmember -- would that get in the way of any future improvements?
- Do I need to add coils to the line to allow flex and if so, how many coils? Seems like I don't want a stiff line since the MC will vibrate independent of the frame and prop. valve

[hdff]

hi, i just bought a 71 short bed and the guy i bought it from did just that. the porportioning valve is just below the front of the cab on the inside of the frame. the only thing i'm not sure of yet is if the hard lines are to close to the header( heat is what i'm thinking of) here is a pic of the engine and you can see the ss flex lines going down to it. i can try to get some other pics later when i get home from work if you would like

[crakarjax]

Originally Posted by hdff

hi, i just bought a 71 short bed and the guy i bought it from did just that. the porportioning valve is just below the front of the cab on the inside of the frame. the only thing i'm not sure of yet is if the hard lines are to close to the header( heat is what i'm thinking of) here is a pic of the engine and you can see the ss flex lines going down to it. i can try to get some other pics later when i get home from work if you would like

Looks nice! Flex lines would alleviate the vibration concern. If you could snap a pic toward the prop. valve that would be great, I'm curious about how the lines leave the valve -- Thanks!

[kwmech]

Originally Posted by crakarjax

I'm redoing all my brakes and lines soon and want to mount the prop. valve on the frame. I've scrounged up all the info I could but didn't find the answers to these questions yet:

- Where is the best place to mount the valve? I read that the later years have it mounted on the frame behind the rad support, but that seems further forward than is necessary. I'm thinking of tucking it in the frame rail just rearward of the front crossmember -- would that get in the way of any future improvements?
- Do I need to add coils to the line to allow flex and if so, how many coils? Seems like I don't want a stiff line since the MC will vibrate independent of the frame and prop. valve

Just rearward of the front x-member is the steering box, that's why chevy put it where they did.

Yes put 2-3 coils in the line for flex.


Personally I like it where it is for convenience, if there is a problem. Nice and easy to get a wrench on the nuts without straining everything

[hdff]

ok i'll jack her up tonite and see what i can get

[brad_man_72]

Mounted mine in the frame behind crossmember a few years ago, no coils, no flex, no problems except one of my other hard lines got a hole in it from being too close to the frame.

[no1udknow]

On the square body trucks they mounted it on the inside of the v shaped front horn support/crossmember, that is where I put mine since the lines were already long enough from the 85 I stole the system from.

here is a pic, just drilled 2 holes and bolted it in place, I did secure the brake lines going across the cross member with a bracket to eliminate vibration.

[no1udknow]

but again, on mine, the prop valve, lines, reservoir and booster are all off an 85. all I had to do was buy and bend a brake line from the coupler in the line running down the passenger side of the frame for the rear brakes, and a reducer/adapter so that line would thread into the much larger hole in the prop valve.

[crakarjax]

Originally Posted by no1udknow

but again, on mine, the prop valve, lines, reservoir and booster are all off an 85. all I had to do was buy and bend a brake line from the coupler in the line running down the passenger side of the frame for the rear brakes, and a reducer/adapter so that line would thread into the much larger hole in the prop valve.

Thanks, I think I'll just route it under the cab to cut down on line length -- plenty of room down there.

Yeah, I like those plastic master cylinders waaaay better than the cast. Might just upgrade to one in the future if I can get it to fit. Can't seem to keep my MC's looking nice, they always rust.

[crakarjax]

Originally Posted by hdff

ok i'll jack her up tonite and see what i can get

Awesome, thanks man!

[hdff]

pics as promised. not the best, kinda hard to get in there

[crakarjax]

Thanks! Finally getting around to this and those pics are priceless!

[RichardJ]

They moved the combination valve (prop valve) to the cross member under the radiator, partly because they moved the disc brake flex lines forward of the suspension. There may already be a pilot hole(s) in the frame where the disc brake lines can go. The drum flex lines were behind the suspension.

The later disc brake, factory steel lines and flex lines fall into place on the 67-72 and attach to the same coupler to the rear, that is under the pass side floor board.
I can't imagine anyone fabricating a make-shift setup when the factory lines are well thought out.
You need to be able to get to the combination valve when bleeding in order to push/pull the metering valve pin, depending on the type you have.

[68C15]

sarcasm<on>

yeah, there's nothing like having something with small rubber seals inside it which is very important to your safety mounted close to a major heat source.

sarcasm <off>

when I changed my front end over with stuff from a 79C10 I placed the combination valve on frame behind radiator. Nice, clean, cool and protected spot for it. Then I ran new lines from master with 3 coils down to top of frame rail to valve.

[notsolo]

You Also may want to consider later model, prop valve Astro vans and S 10's have a bracket that bolts to the The Master cylinder /Booster and hangs right under it.

[dirtyjim]

my prop valve is mounted to the frame in the stock 73+ location. used the factory brake lines from the mc to the prop valve from a mid 80's truck and bent and flared the rest of the lines to fit. you can use the complete 73 up front brake lines and hoses by drilling the holes in the frame so they can pass through in front of the crossmember, I used early 70's el camino brake hoses in the factory location behind the crossmember.

the only thing I would do differently is fab up an angle bracket to go between the prop valve and frame to tilt the top of the pro valve out about 3/4" away from the frame for better clearance on switch for the centering valve