Master cyclinder question?
Elder User
Joined: May 2009
Posts: 729
Likes: 0
From: Peoria, Arizona
Yes you still need a proportioning valve. front brakes do most of the stopping and require more pressure. Without a Proportioning Valve in the system, both the front and rear brakes receive the same pressure. This will cause the rear brakes to lock up long before the front brakes are engaged enough to stop the car. The Proportioning Valve allows full pressure to the front brakes and dampens the pressure to the rear brakes, allowing the correct pressure so both can stop equally.
I dont know about a bolt in 1951 dual master. I do know that some MC come pre valved.
I dont know about a bolt in 1951 dual master. I do know that some MC come pre valved.
Lead Driver
Joined: Apr 2002
Posts: 8,813
Likes: 13
From: Littleton, New Hampshire
Finding a bolt-on MC for 4-wheel disc brakes is a tall order. As far as I know there isn't such an animal. You will need to use a MC from some application that comes with 4-wheel discs. Most kits use the Corvette MC but there are others. This type MC would require no residual valves. The proportioning valve is optional. Pickups are lighter in the rear than the front so a proportioning valve might be a good idea but I am unsure how it might work will four wheel discs. This will definitely be either a kit or you will have to fabricate something yourself. I assume you are still using an under the floor system since you wanted a bolt-on MC. To keep that system a kit will probably be necessary. If you go with a firewall mounted MC it would be easier to fabricate... 
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Senior User
Joined: Nov 2010
Posts: 133
Likes: 0
I have heard about the corvett MC and I will look into that. I am going to use the original brake pedal, so yes it will be under the floor. I have an apportionate valve from the donor 1984 F-150, but it had drum back and disc's front. Not sure how all that will work. The Corvett MC, not sure if I would need a apportionment valve or not.
More research I guess.
Thanks for the input.
More research I guess.
Thanks for the input.
Elder User
Joined: May 2009
Posts: 729
Likes: 0
From: Peoria, Arizona
the ratios will be off if the valve was meant for disc drum. Drum brakes are self energized and require less pressure then disc brakes do.
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Fleet Mechanic
Joined: Apr 2008
Posts: 1,373
Likes: 6
From: Moore (or less), OK.
Is your master cylinder still under the floorboards or have you moved it to the firewall? Mine is moved to the firewall and I am using a Wilwood tandem MC on a power booster. 4 wheel discs and the Wilwood proportioning valve.
With the MC on the firewall you do not need the residual pressure valves to maintain line pressure like you do with the under floor unit.
With the MC on the firewall you do not need the residual pressure valves to maintain line pressure like you do with the under floor unit.
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Senior User
Joined: Nov 2010
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The MC is going to be under the floor, however now I think I see with disc's all around I need to go to an adjustable apportionment valve. Starts to get complicated to say the least.
Thanks for your input.
Thanks for your input.
Cargo Master
Joined: Feb 2008
Posts: 2,793
Likes: 128
From: Windermere Valley,B.C. Ca
Fleet Mechanic
Joined: Apr 2008
Posts: 1,373
Likes: 6
From: Moore (or less), OK.
I have the Wilwood Forged Dynalite calipers front and rear. It's a matched system with 4 sq" area on the front pistons and 3 sq" area on the rears. With the Wilwood tandem circuit MC putting out a 2 to 1 ratio between the front to rear circuits it still needs a proportioning valve to lighten the rear circuit pressure and keep it from locking up the rear end first.
I wouldn't put the system on a pickup without a proportioning valve and, if you run the MC under the floor you need the residual pressure fittings to maintain line pressure. 2 psi for disc and 10 psi for drums. Without them the pressure would bleed off and it would take a few pumps to get brake pressure up enough to stop you.
I wouldn't put the system on a pickup without a proportioning valve and, if you run the MC under the floor you need the residual pressure fittings to maintain line pressure. 2 psi for disc and 10 psi for drums. Without them the pressure would bleed off and it would take a few pumps to get brake pressure up enough to stop you.
Posting Guru
Joined: Mar 2010
Posts: 1,781
Likes: 6
From: WEWAHITCHKA FL.
MC
I have 4 wheel disk with the MC under the floor. Got it from classic haulers. The valve thingie is built in . I bought a torino 11' disk setup that had the e brake built in . I didn't hook the e brake up due to i needed the cab room for my leg. I couldn't get any brakes till i changed the rear calibers to a front malibu with out the e brake. You will NOT get brakes until you do this OR hook the e brake up.