Brake Help
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More Turbo
Joined: Jun 2020
Posts: 554
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Brake Help
Hey all,
recently converted to a dual master cylinder and power brakes. I got everything bled and adjusted all four to have a slight drag. Only thing is that I can’t get the fronts to lock up under hard braking. Pedal isn’t soft by any means.
many help/advice? Aside from it not locking all four, the truck brakes better than before it feels like. And I don’t have the booster hooked to manifold vacuum yet.
1966 F100 drums in all four corners
recently converted to a dual master cylinder and power brakes. I got everything bled and adjusted all four to have a slight drag. Only thing is that I can’t get the fronts to lock up under hard braking. Pedal isn’t soft by any means.
many help/advice? Aside from it not locking all four, the truck brakes better than before it feels like. And I don’t have the booster hooked to manifold vacuum yet.
1966 F100 drums in all four corners
Cargo Master
Joined: Jul 2006
Posts: 3,014
Likes: 91
From: Concord, CA
First, did the rears lock up since they would be the first to do so and then you would adjust pressure differential so they all lock up at the same time. Locking up has little to do with the adjustment of the shoes unless you were wildly off on some.
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More Turbo
Joined: Jun 2020
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Yes I could. The new MC is a new made one for a 67-72 truck, 1in bore. So everything should line up since the original mc was also a 1in bore.
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Lead Gopher
Joined: Aug 2012
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From: Seattle
I can find at least 6 different master cylinders that Ford used for Drum/Drum systems between 1967 and 1972. Some of them used different length push rods. What push rod are you using? The one your truck came with like this one in the picture? This one is 4 31/32" center length. Just thinking if there's a chance it needs a bit more length to reach full fluid movement.
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More Turbo
Joined: Jun 2020
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Yes the rear port is hooked to the front brakes. The pushrod is adjustable, I adjusted the pedal so it’s just touching the bump stop, the pushrod from the truck is not usable because brackets for the booster push it out further from the fire wall.
More Turbo
Joined: Dec 2019
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From: Orange County
Cargo Master
Joined: Jul 2006
Posts: 3,014
Likes: 91
From: Concord, CA
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More Turbo
Joined: Jun 2020
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Added more lash and same thing. Again with the prop valve, why would it be needed? The bore size and size of lines are the exact same as original, so there should be no need for it, and Ford didn’t have one originally, and these are drum brakes all around.
More Turbo
Joined: Dec 2019
Posts: 734
Likes: 154
From: Orange County
I forgot you have a booster. As tbm3fan points out, the stub out of the booster needs to be the right length so it's not holding the MC open, and also pushing it full travel. You might want to double check that is set correct.
About the proportional, my modified truck needs one, otherwise the rears will lock up very early. I think it might be a function of the large tires, heavy engine, short wheelbase.
I've never heard this, but I'm wondering if there is something about wheel cylinder bore diameter, and brake shoe size, and balance between front and rears on a single pot vs dual pot. A basic schematic of the hydraulic systems are pretty equivalent, but not the same.
Do you know how your brakes compare to a 1967 drum / drum truck?
About the proportional, my modified truck needs one, otherwise the rears will lock up very early. I think it might be a function of the large tires, heavy engine, short wheelbase.
I've never heard this, but I'm wondering if there is something about wheel cylinder bore diameter, and brake shoe size, and balance between front and rears on a single pot vs dual pot. A basic schematic of the hydraulic systems are pretty equivalent, but not the same.
Do you know how your brakes compare to a 1967 drum / drum truck?
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