Porportioning Valve Position ??

Discussion in '1960-1966' started by Ratnest, Jan 16, 2014.

  1. Ratnest

    Ratnest Member

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    Yesterday I starting running the brake and fuel lines in my 66 chassis. (I don't have the cab back yet.) I'll be using the booster, dual M/C, and porportioning valve off a junk yard 93 Jeep Cherokee. I'm considering mounting the por. valve on the driver's side frame rail just forward of the front shock upper mount. That way it will be out of sight, but easy to plumb to the brake lines and M/C.

    I'd sure appreciate a little feedback and/or suggestions. Thanks.:confused:
     
  2. Rich 5150 69

    Rich 5150 69 Member

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    I don`t see any issues with that, not sure or not that the distance from the master would affect it, I have not ever read anything on it.
     
  3. Ratnest

    Ratnest Member

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    Thanks...I've seen them farther from the M/C than mine will be. I'm guessing my valve will be 3-4 feet away from the M/C. Maybe Lakeroadster will chime in.
     
  4. Lakeroadster

    Lakeroadster Member

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    Ratnest,

    What do you have for brakes, drum-drum or drum-discs?

    I've found this website to be very helpful: http://www.hot-rod.com.au/builder/brakes.html

    I prefer to us an adjustable proportioning valve. On my 2 old Hot Rods (Drum- Disc set-up) I mounted the adjustable proportioning valve on the inside of the frame rail near the rear axle. The adjustable valve allows you to dial in the rear brakes so they lock up before the front brakes.

    The problem I see with using a 93 Jeep Cherokee valve is it's not from a truck. SUV's are heavier in the back than a pickup, so the front to rear ratio may not work very well on your pickup.

    At least that's my 2 cents.

    Hope that helps.

    John
     
  5. Rich 5150 69

    Rich 5150 69 Member

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    You need need to review that, thats wrong...
    It is critical that the rear brakes do not lock up first under any circumstances since this could lead to a loss of control. Obviously, with enough brake pressure, all four wheels can lock up, but we are looking for the rears to lock up only after the front brakes do.
     
  6. Lakeroadster

    Lakeroadster Member

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    Wrong? Hmmmm :rolleyes: What we have here is a difference of opinion.... I am merely basing my comments on my own personal experiences. I am however always open to learning from others experiences, even though I am an old dog :D

    In my experience, driving pickup trucks most of my life in climates with four seasons, the rear tires are the first to lock up. And when they do I can still steer the truck.

    When the front brakes lock up first you have now lost the ability to steer, you're along for the ride.
     
    Last edited: Jan 17, 2014
  7. Ratnest

    Ratnest Member

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    Thanks guys for the input.

    The 66 brakes are disc front and drums rear. The 93 Cherokee had the porportioning valve literally hanging right below the M/C, being supported by the hard brake lines. It was an ugly setup and that's one of the reasons I planned to put the por. valve out of sight.

    I printed off the brake info on the website Lakeroadster listed and will study it. It could be that I may need a residual valve in the 66's system to get proper braking balance.
     
  8. Lakeroadster

    Lakeroadster Member

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    The proportioning valve may already have the residual valve in it? That's why I don't like using the factory prop. valve... 'cause I don't know what's in it.
     
    Last edited: Jan 17, 2014
  9. Rich 5150 69

    Rich 5150 69 Member

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    We`re only talking milliseconds here John, with the rear locking way in advance of the front the backend will want to swing around, especially with a truck with the weight differential, even with steering available on a wet surface that will become the wild ride..
    Prop valve 101
    http://www.chevyhiperformance.com/techarticles/71398_install_brake_proportioning_valve/
     
  10. Ratnest

    Ratnest Member

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    I did a quick read on the above tech article. I will consider getting one of the adjustable valves if it's not too costly. That way I could toss the Jeep porportioning valve.
     
  11. markeb01

    markeb01 Member

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    When I swapped in a 1975 front suspension on my 1960, I used the stock 75 prop valve. I mounted mine on the back side of the front crossmember, directly below the driver side motor mount tower. Completely out of sight and with enough bends in the hard lines, coils of tubing aren't required to avoid vibration fractures.

    [​IMG]

    [​IMG]
     
  12. Ratnest

    Ratnest Member

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    Thanks for the info....a nice looking set-up.
     
  13. Dougs55

    Dougs55 Member

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    Porp Valve

    Got another question along the same lines. I put in all the new brake stuff and replaced the manual MC with a power brake set up. The MC came with a porp valve but decided to leave the one that was already there mounted down on the frame.
    Sitting in the truck without the engine running I have brakes but as soon as I start it up they go all the way to the floor?
    I used a good vacuum pump to thoroughly bleed the entire system from each wheel so I doubt that it is air in the lines. Is it the porp valve that I need to change out or I am I doing something else wrong?
     
  14. Rich 5150 69

    Rich 5150 69 Member

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    See the above pic from Mark, the black cover on the front of the prop valve there is a button under this cover, a lot of times you have to depress this button to get the air out of the valve while bleeding system, you will have to start over to be sure, you probably still have air in it, if not then we will look for other issues
     
  15. Lakeroadster

    Lakeroadster Member

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    If the brakes are good until you start the engine wouldn't logic dictate that the problem has to be related to the power brake booster?

    I'd suggest emailing or calling Vince Bunting at CH Topping & Company: http://www.chtopping.com/Home/index.html

    They helped me with the brakes on my Hot Rod Model T RPU. Nice folks too.
     
    Last edited: Jan 21, 2014
  16. Rich 5150 69

    Rich 5150 69 Member

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    Here`s a good site as well..
    http://www.mpbrakes.com/docs/troubleshooting/troubleshooting-chart.pdf

    The reason behind the button on the prop valve is that if the valve is not centered you will not get all the air out of the master cylinder therefore the master will just go to the floor, also line hookup is shown below.
    Here`s a good read from Rick L on Chevy talk forum...note bold line..
    If it is a C3 Corvette master cylinder, it is for disc/disc, as that's the only way those were equipped.

    The C3 Corvette master cylinder has two large reservoirs. Disc/drum master cylinders from the early 70s cars (like the 71/72 Chevelle m/c sold by many for conversions) have a large reservoir for the front discs and a small reservoir for the rear drums. The reason that disc brakes have large reservoirs is that usually have no adjuster mechanism and don't need it because there are no springs to push the piston and hardward back. So as the pads wear, the fluid level in the master cylinder drops. A big reservoir simply means that the owner can be lazy and not have to check or replenish the brake fluid. There is no downside to having a large reservoir with drum brakes. The only reason you wouldn't want it is that the disc/disc master cylinder is longer and it might not fit in some applications. Likewise you can run a small reservoir master cylinder with no ill effect with discs, you just have to pay more attention to fluid level.

    The other thing about drum brake dual master cylinders is that the 67-70 models had a residual pressure valve in the master cylinder outlet port for drum applications only. This keeps a high pedal for drums, but it's not wanted on discs as they will cause the brakes to drag. When GM went to the combination valve on the 1971 models they put the residual valve in the combination valve for disc/drum applications. So 1971 and later master cylinders won't have residual valves. So there's no difference between disc and drum there.

    Last thing, manual brakes need a smaller bore master cylinder than power brakes. On the 60s and 70s master cylinders we normally use for brake upgrades, manual brakes need a 1" bore and power brakes need a 1-1/8" bore.

    So, your master cylinder will be just fine no matter what rear brakes you choose. If you use a combination valve, you should choose disc/disc or disc/drum depending on which you have. I think you should be using one with disc/drum.

    There is no reason for you to switch to rear discs unless you want them. You just need to be sure your rear drum setup is fully functional. The rear disc conversions that use the Caddy calipers can be temperamental with regard to the e-brake.
    I have read that to tell whether or not you have a residual valve in the master cylinder is to look at the ports, if there is a brass fitting in there it has the valve, to remove it all you have to do is use a sellf tapping screw thread it into the hole of the valve and use a screw driver to pull it out
     

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    Last edited: Jan 22, 2014
  17. Ratnest

    Ratnest Member

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    Following advice and research, I chose to run the 93 Cherokee porp. valve rather than an adjustable valve. I can go to the adjustable later if needed. I liked the mounting technique used by markeb01 and stayed with my plan to attach it to the frame near the M/C.

    Here are a couple photos of the porp. valve, a junk yard crossmember I used to mount the TH350, and a fun photo that makes me wonder if my SBC "will be a dog":D
     

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