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pictured below. Replaced the lines, brakes, wheel cylinders forward of the rear axle, so the back brakes, lines cylinders are untouched so far. Forward reservoir is attached to forward brakes, rear attached to rear brakes. All 4 corners are manual drums. Front brakes bled and adjusted. Took it for a short spin and I barely had any grab with the forward brakes, I could get the back to lock up pretty easy but nothing from the fronts and braking as a whole is much worse than before swap. Front wheel cylinders are 1 1/8 and rears are 7/8 bore size.
My question is, do I need a proportioning valve, brake differential valve, something else? Any suggestions ideas for specific parts much appreciated, I'm running out of rope here.
Replaced the lines, brakes, wheel cylinders forward of the rear axle, so the back brakes, lines cylinders are untouched so far. Forward reservoir is attached to forward brakes, rear attached to rear brakes. All 4 corners are manual drums. Front brakes bled and adjusted. Took it for a short spin and I barely had any grab with the forward brakes, I could get the back to lock up pretty easy but nothing from the fronts and braking as a whole is much worse than before swap. Front wheel cylinders are 1 1/8 and rears are 7/8 bore size.
My question is, do I need a proportioning valve, brake differential valve, something else? Any suggestions ideas for specific parts much appreciated, I'm running out of rope here.
Amazon find
Is this power or manual?
Regardless, it sounds as if the MC push-rod length is incorrect so as not to push both MC pistons travel as needed.
No valving need on a drum/drum application (other than a pressure differential valve might be helpful).
EDIT - (Fr. for additional information)
Forward reservoir is attached to forward brakes, rear attached to rear brakes.
You also have it plumbed in backwards. The PRIMARY RESERVOIR (nearest push-rod) operates front brakes, SECONDARY RESERVOIR operates rear brakes.
Removed the original flower pot master cylinder and installed this bad boy, https://www.amazon.com/Dorman-M39495...eywords=M39495 pictured below. Replaced the lines, brakes, wheel cylinders forward of the rear axle, so the back brakes, lines cylinders are untouched so far. Forward reservoir is attached to forward brakes, rear attached to rear brakes. All 4 corners are manual drums. Front brakes bled and adjusted. Took it for a short spin and I barely had any grab with the forward brakes, I could get the back to lock up pretty easy but nothing from the fronts and braking as a whole is much worse than before swap. Front wheel cylinders are 1 1/8 and rears are 7/8 bore size.
My question is, do I need a proportioning valve, brake differential valve, something else? Any suggestions ideas for specific parts much appreciated, I'm running out of rope here.
Amazon find
If that is a typical Ford master cylinder I believe you have the lines backwards. The front reservoir should be for the rear brakes. Take the cover off and see if the reservoirs are different sizes the larger one is the front brakes. You should not need a differential or proportioning valve for it to work.
Removed the original flower pot master cylinder and installed this bad boy, https://www.amazon.com/Dorman-M39495-Brake-Master-Cylinder/dp/B001PYNYBW/ref=sr_1_1?s=automotive&ie=UTF8&qid=1537931435&sr= 1-1&keywords=M39495 pictured below. Replaced the lines, brakes, wheel cylinders forward of the rear axle, so the back brakes, lines cylinders are untouched so far. Forward reservoir is attached to forward brakes, rear attached to rear brakes. All 4 corners are manual drums. Front brakes bled and adjusted. Took it for a short spin and I barely had any grab with the forward brakes, I could get the back to lock up pretty easy but nothing from the fronts and braking as a whole is much worse than before swap. Front wheel cylinders are 1 1/8 and rears are 7/8 bore size.
My question is, do I need a proportioning valve, brake differential valve, something else? Any suggestions ideas for specific parts much appreciated, I'm running out of rope here.
Amazon find
I don't think you need a proportioning valve with all drums. But I've always seen the front chamber go to the rear brakes and the rear chamber go to the front brakes. I really don't know why that would make any difference either on all drum brakes.
I was under the impression all four wheel cylinder bores should be the same size. That may be your problem. Or maybe I'm mistaken.
EDIT: I am mistaken. On my 65 F250 2WD all drum brakes, the front wheel cylinders are 1 1/8" bore and the rears are 1" bore.
Removed the original flower pot master cylinder and installed this bad boy, https://www.amazon.com/Dorman-M39495-Brake-Master-Cylinder/dp/B001PYNYBW/ref=sr_1_1?s=automotive&ie=UTF8&qid=1537931435&sr= 1-1&keywords=M39495 pictured below. Replaced the lines, brakes, wheel cylinders forward of the rear axle, so the back brakes, lines cylinders are untouched so far. Forward reservoir is attached to forward brakes, rear attached to rear brakes. All 4 corners are manual drums. Front brakes bled and adjusted. Took it for a short spin and I barely had any grab with the forward brakes, I could get the back to lock up pretty easy but nothing from the fronts and braking as a whole is much worse than before swap. Front wheel cylinders are 1 1/8 and rears are 7/8 bore size.
My question is, do I need a brake pressure differential valve?
ALL 1967 and later F100/350's with a dual master cylinder have a Brake Pressure Differential Valve that some people call a proportioning valve.
The valve is different with drum vs disc brakes. 1967/74 2WD different than 4WD. Some 1975/79 4WD's use a different valve than 2WD's.
See basic part number 2B257 = Here are the 1967/72 applications. Note that 1967's are 1967 only.
I don't think you need a proportioning valve with all drums. But I've always seen the front chamber go to the rear brakes and the rear chamber go to the front brakes. I really don't know why that would make any difference either on all drum brakes.
No proportioning valve on four wheel drum.
I was under the impression all four wheel cylinder bores should be the same size. That may be your problem. Or maybe I'm mistaken.
The differing wheel cylinder size(s) and lining size(s) were used for balanced braking (front-rear bias) before disc brakes made valving actually necessary. The front brakes do most of the braking.
BUT -GM/BENDIX did use valving on some of it's drum brake cars and if you actually read the theory and cipher on it might come to a different realization. But don't let this comment (which I shouldn't have added) confuse anyone that I am recommending the use of valve(s). FOMOCO did not.
What the OP problem is plumbing and maybe push-rod adjustment.
Wow thanks for the support! I'll swap the lines this evening and report back. As for the pushrod length, I did have to shorten the shorter of the two pushrods that the MC came with. I trimmed it until it would install without putting any pressure on the MC and then took off just a bit more. Total of about 3/16" removed.
I just did this swap myself. Curious to know if swapping the lines helped... my brakes are working fine IMHO, but according to this thread I have them to the wrong reservoirs.
I also had to shorten my plunger, but again, my brakes seem to be fine.
Bill, the differential valves depicted in the 69 shop manual for drum brakes are nothing more than a switch to turn the warning light on if a part of the system fails. They don't meter the fluid like a proportioning valve.
No valving need on a drum/drum application (other than a pressure differential valve might be helpful).
It's situations as this where I can get my self into more trouble ...
There is a huge difference in the two valves, PRESSURE DIFFERENTIAL and PROPORTIONING VALVE.
There is no need for either valve on this particular retro-fit. Now, that being said, when the DUAL PISTON MC came into use (Federal Mandate) it included a device to let the driver know that there was a system(s) failure. This was called the PRESSURE DIFFERENTIAL VALVE and was remotely located away from the MC. If any pressure loss was detected by this valve in the dual system it would illuminate a warning lamp to hopefully make the driver aware.
Without the lamp, the failure(s) (if not an immediate total failure) may accelerator as to lead to a complete brake failure without any prior warning or brake loss indication. It was included for your (and others) safety.
Remember, if you have only one side of the system to fail, you have to stop the vehicle with either front or rear braking. It is not designed to allow you to continue to drive but rather able to slow/stop the vehicle without running over something.
Also, Bill understands the difference. What he is attempting to point out is FORD's mis-characteration of the proper naming of valving in it's PARTS CATALOGS leading to confusion with the parts dude and mechanics.
Bill, the differential valves depicted in the 69 shop manual for drum brakes are nothing more than a switch to turn the warning light on if a part of the system fails. They don't meter the fluid like a proportioning valve.
The Low Brake Fluid Warning Lamp Switch threads into the Brake Pressure Differential Valve. It's this: C8AZ-2B264-A
1965 F100 Dual Master Cylinder Upgrade, front brakes not working
