Dual chamber master cylinder for drum brakes

[Lamar Wadsworth]

Need to replace the master cylinder on my '55 Ford. Keeping stock drum brakes. Is there any particular late '60s-early '70s dual chamber MC for drum brakes that someone can recommend that you have used in this application? I think dual chamber MCs became standard on everything around '66 or '67. I remember a '69 Dodge A-100 van and a '72 Ford pickup I had both had dual chamber MC, drum brakes all around, and no power booster. Wondering if one of those might work, or something for a mid-size Ford car of that vintage? I can do the brake line plumbing to separate front and rear brakes. I know Rambler was the first to have that feature in the early '60s.

[fordor41]

I would think a 70's Mustang would work. just make sure bore is same diameter. If you have a non-power M/C now, stick with non-power M/C as the pocket in the cylinders are different between power and non-power.I don't know why a dual M/C for disc in the front wouldn't work if that's all you can find. may want to add a 10# residual in the front(disc take 2#)as some dual drum/disc M/c's have internal residual valves (2# &10#) and would have wrong RPV for front drums

[JeffB2]

Originally Posted by Lamar Wadsworth

Need to replace the master cylinder on my '55 Ford. Keeping stock drum brakes. Is there any particular late '60s-early '70s dual chamber MC for drum brakes that someone can recommend that you have used in this application? I think dual chamber MCs became standard on everything around '66 or '67. I remember a '69 Dodge A-100 van and a '72 Ford pickup I had both had dual chamber MC, drum brakes all around, and no power booster. Wondering if one of those might work, or something for a mid-size Ford car of that vintage? I can do the brake line plumbing to separate front and rear brakes. I know Rambler was the first to have that feature in the early '60s.

The one we have used over the years in the HAMB 1952-59 Ford Group is the Autozone M1485 this is a rebuild unit,so why a rebuilt you ask ? A lot of these are USA made Bendix or Raybestos castings which are better than the offshore new ones made in India or China if they have a few in stock look for the Bendix on the underside. This is listed for 1967-68 Mustangs with drum brakes. Here is a NOS one so you can compare. https://www.ebay.com/itm/NOS-67-70-F...-/402045990606 WARNING ! Do Not use the pushrod that comes with some of these, you should use your stock 1952-56 push rod. The push rod that comes with some of these has a clip that will lock it in place,removing one is pure Hell you can also toss that clip off the end too.

[KULTULZ]

...may want to add a 10# residual in the front(disc take 2#)as some dual drum/disc M/c's have internal residual valves (2# &10#) and would have wrong RPV for front drums

A #2 RPV (Residual Pressure Valve) is used only on a DISC BRAKE CIRCUIT if the MC is located under the front caliper, say a 56 F100. It prevents fluid drain-back from the caliper to the MC at rest leading to a spongy pedal.

If you buy a late replacement MC, it will not likely have #10 RPV(s) installed. You then must plumb in inline RPV's to both circuits..

I don't know why a dual M/C for disc in the front wouldn't work if that's all you can find

Differing bore sizes and fluid pressure/volume.

[KULTULZ]

Originally Posted by JeffB2

Do Not use the pushrod that comes with some of these, you should use your stock 1952-56 push rod. The push rod that comes with some of these has a clip that will lock it in place,removing one is pure Hell you can also toss that clip off the end too.

AMEN!

BTW - That clip is available and has an important function.

If I were to do a conversion today, I would find a correct take-off and have it sleeved/rebuilt. The RPV's used to come in the FORD rebuild kits.

[Lamar Wadsworth]

Sponsored Links (Register now to hide all advertisements)

Good info, thanks!

[frnkeore]

Regarding the PB MC, the main difference, is in the diameter of the piston. On most Ford's, up until at least '70, the non PB unit, had a 1" piston, the PB, had 7/8".

The smaller piston, will give you higher pressure, to the wheel cylinders but, with a little more brake pedal travel.

[40 Deluxe]

Originally Posted by Lamar Wadsworth

Need to replace the master cylinder on my '55 Ford. Keeping stock drum brakes. Is there any particular late '60s-early '70s dual chamber MC for drum brakes that someone can recommend that you have used in this application? I think dual chamber MCs became standard on everything around '66 or '67. I remember a '69 Dodge A-100 van and a '72 Ford pickup I had both had dual chamber MC, drum brakes all around, and no power booster. Wondering if one of those might work, or something for a mid-size Ford car of that vintage? I can do the brake line plumbing to separate front and rear brakes. I know Rambler was the first to have that feature in the early '60s.

Make sure you will have sufficient pedal travel to completely bottom out the piston(s) in the master cylinder. Check before adding the brake fluid.

When you lose fluid/pressure on one side of a dual master cylinder the pedal will go almost completely to the floor before any braking action occurs. If the linkage is not engineered right, the pedal may hit the floor before the piston in the master cylinder travels far enough to apply the brakes.
When all is buttoned up and bled, crack a bleeder screw loose on a rear wheel cylinder and see if you can stop (don't do this in the garage in front of your work bench!). Close the rear bleeder and repeat on the fronts. Rebleed if necessary.

[34pickup]

1967 Fairlanes also had dual master cylinder drum brakes. Except the GT that had disc fronts.

[JimNNN]

It sounds like you're getting some solid leads, Lamar. I put a dual reservoir on my '54 wagon with drum brakes maybe 8-10 years ago. I don't remember where I got it, or if the '54 application will work for '55, but if you strike out on your leads, pm me and I'll try and track down the receipt, which I'm pretty sure I still have. I won't bother looking until you need the info, though.


I know I bought it as something that was marketed as an upgrade to 2 reservoir for '54 Fords, so it wasn't some crap shoot engineering effort. It's worked good over the years.

[KULTULZ]

The period DUAL RESERVOIR MC(s) you want are 1967-1973 FORD INTERMEDIATE (FAIRLANE-MUSTANG).

DRUM/DRUM and DISC/DRUM are included for availability I had the chart (from the 1965/1972 MPC), that shows application, manual/power and bore size. The text would also include info regarding the valving used in the period.

I have a current computer problem(s) and will post that info as soon as I can.

If you buy a current production replacement MC, it will most likely not have the RPV(s) in the outlet circuits. You will have to plumb inline valves.

[JimNNN]

Lamar, I got your message, but don't think my messages are getting back to you. I can't find my receipt, but will take a pic of what I've got and send it to you. I'd bet KULTULZ's recommendation is the way to go. He's kinda the man around here. Nevertheless, I'll get a pic of what I've got to you, if I can.

[KULTULZ]

Just a warning, beware of these so-called disc brake changeover vendors. Few seem to have full comprehension and now are supplying off-shore parts.

Case in point, this individual went to an EvilBay vendor with a four wheel manual drum pickup and talked to the guy. Said he wanted power dual reservoir drum for now but would like to add front disc later.

Below are photos of what he was sold and installed-

Now he has to can it and start over.

[Flattop]

What style residual pressure valves (rpv’s) are you using?

[V8 Bob]

Originally Posted by KULTULZ

Just a warning, beware of these so-called disc brake changeover vendors. Few seem to have full comprehension and now are supplying off-shore parts.

Case in point, this individual went to an EvilBay vendor with a four wheel manual drum pickup and talked to the guy. Said he wanted power dual reservoir drum for now but would like to add front disc later.

Below are photos of what he was sold and installed-

Now he has to can it and start over.

All he has to do is switch the lines going into the combo valve, so the secondary (smaller) rear brake M/C chamber goes between the prop valve adjuster and pressure switch, and the larger front M/C chamber goes to the front of the pressure switch with the two output ports. When front discs are installed, removal of the red 10 lb residual is all that's needed.

[KULTULZ]

Originally Posted by V8 Bob

All he has to do is switch the lines going into the combo valve, so the secondary (smaller) rear brake M/C chamber goes between the prop valve adjuster and pressure switch, and the larger front M/C chamber goes to the front of the pressure switch with the two output ports. When front discs are installed, removal of the red 10 lb residual is all that's needed.

Why would one install an ADJUSTABLE BRAKING BIAS VALVE on a four wheel drum application? All he wanted was a split reservoir w/ booster. Did the vendor a$$-u-me the secondary circuit has an internal RPV? What about MC bore size?

All replacement MC's for that period do not include RPV(s) as later applications (1974- ) did not use an RPV and the deletion reduces inventory.

You see value in what he was sold? You would modify yours or a customers car in such a manner?

[V8 Bob]

KULTULZ,
You're right. I somehow confused this thread with one where front discs were going to sometime replace the drums. My bad!

[KULTULZ]

You're OK ...

The buyer stated to the vendor that he was considering a disc upgrade in the future ($$$) and for now only wanted a boosted split system and instead of the vendor supplying only the correct drum system upgrade sold him a system which is totally unsafe.

HEY! Anytime you see or feel I have posted something incorrect, feel free to correct. I am not proud and learn something new everyday even on older vehicles.

I was starting to have self-doubt there.

[KULTULZ]

Originally Posted by Flattop

What style residual pressure valves (rpv’s) are you using?

Sorry about that.

Inline (after MC) valves. They should be mounted as near the MC as possible.

[V8 Bob]

Originally Posted by KULTULZ

You're OK ...

The buyer stated to the vendor that he was considering a disc upgrade in the future ($$$) and for now only wanted a boosted split system and instead of the vendor supplying only the correct drum system upgrade sold him a system which is totally unsafe.

HEY! Anytime you see or feel I have posted something incorrect, feel free to correct. I am not proud and learn something new everyday even on older vehicles.

I was starting to have self-doubt there.

I have to disagree with you on the system being totally unsafe. The only thing unsafe was the incorrect M/C plumbing, as I pointed out earlier. I would have also included an adjustable proportioning valve with the intent to upgrade the front drums to discs, minimizing additional plumbing changes and costs later on.

As far as the proportioning valve, turning the knob CW to fully open the valve raises the split point about 1000-1200 psi, well above the normal drum brake operating pressures-in effect bypassing any proportioning to the rear drums.