Im getting ready to install the small bolt disks on the front of my 60 Valiant and have procured a new manual master cylinder for a 73 duster with disks and a adjustable prop valve for the rear brakes and was wondering if I can just block the port for the rear brakes and plumb the rear line into the front resivoir with the adjustable prop installed inline?
Also can I use the front lines as is,what i mean by that is that the right hand front line runs up the left rail across the bottom of the radiator support and back down ththe rightside to the brake or do i need to run the line across the firewall like later disc -drum setups.I really hate to change this as the old dude that had the car before me replaced all the lines with new stuff.Thanks in advance.
HyperValiant

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1960 Hyper-Pac Valiant(rolling test-bed)
1963 Valiant V2OO(Son's summer project,- he just turned 15 )
1972 Valiant 4dr(Daughter Kelly's repair in progress)
1974 Valiant (v8) daughter Kelly's work in progress

Brake line routing doesn't really matter, I wouldn't worry about it as long as there are no leaks.

I would not plumb the system like you are describing. That renders half of the master cylinder useless, and makes the entire system as reliable as the single resevoir master... loose the fronts, or the rears, and you have none at all.

not only that it defeats the whole purpose of the prop valve altogether.

The proportioning valve is there to ensure that the rear brakes are applied more lightly than the front, because during a stop weight comes off the rear wheels and is transferred to the front. If the rears got equal pressure as the fronts they would just lock up and your rear end would swing around dangerously. If youre switching to a dual circuit master your lines have to be plumbed as such. Whether the lines go across the firewall or under the rad support isnt important as much as the lines for each circuit being close to or equal in length. Brake fluid doesn't compress much when pressure is applied to it, but if one line is much longer than the other, then the short line will apply the brakes first, causing uneven braking. Oh, and also check to see that there is a coil of brake line of maybe two or three turns where they connect to the master, this is important for absorbing flex and vibration between the master and the proportioning valve. Without it you would get metal fatigue in the brake lines and they would harden and crack, usually at the fitting.

Also, since the prop valve kind of connects the front circuit to the rear to do its job, when one circuit loses pressure there is a valve inside that shifts over, sealing the good circuit from the bad and closing a switch that illuminates a brake warning light. Good thing to have.

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Thanks guys,Ive got a 80 Cordoba prop valve, would that be appro
priate for my setup?
HyperValiant

Hyper,

I believe what you were describing originally would work. Just run the front reservoir directly to the rear brakes via the adj prop valve, and run the original single-pot line to the rear reservoir. The only issue is blocking the original rear line port on that block. I may try this on my '66 Valiant. Otherwise, the 'doba valve should be fine with the adj prop in the rear line.

Lou

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Home of Slant6-powered fun machines since 1988

I'm planning on the disk conversion in the near future. In the meantime I installed a duel MC with the lines routed as Lou described and kept the front drums.

I simply plugged the rear line in the original single pot MC block and ran the rear line through a summit adjustable valve.

With the adjustable vale I can set the rear brakes as needed.

Good Luck,

John Killin

wow, I missed the word "adjustable" altogether. You are correct, you can use the prop valve to adjust bias on one circuit and run the other circuit direct.

Sorry guys!

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.