Dual Master Cylinder for 1963 Falcon

CoupeBoy

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I'm working on a 1963 Falcon Convertible
1963.5 Falcon Convertible Build -- FordSix Forum
I probably should skip straight to disk/drum setup, but I've always wanted to test out drilled drums.. so I'm going to waste some time and money by rebuilding the stock drum/drum setup.
It has 2.25" front drums and 1.75" rears. At first I was just going to order up a replacement 1968 Mustang MC, figured I could keep it interchangeable with my Mustang.
But then I started thinking, always dangerous, what if there is a different reservoir that has a larger bore that would decrease the required brake pressure.

So how about it, anybody have a recommendation for which Master Cylinder to use?

Also I am still interested in looking at any articles on how change from a pressure actuated brake light switch over to a pedal mounted switch like they did on newer cars.

TIA
-ron
 

CoupeBoy

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Most articles I've read say '67 or '68 Mustang, bolt it in, do a little plumbing work and call it good.
Most say that the I want to reuse the original pushrod.
Most say that all ford master cylinders are interchangeable (bolt pattern).
And it is also recommended to install an adjustable brake proportioning valve to get maximum braking from the rear.

I got curious to see what else was available..
so I poked around on the O'Reilly's Auto Parts Website
Original Falcon fruit jar had a bore of 1.0", although they also list a 0.875". I assume the smaller one is for the i6 cars with the 9" drums vs the 10" drums on the SBF cars.

This is what they found.

Their brand is called BrakeBest
Stock Falcon
10-32900 1" bore
10-39626 0.875" bore

1968 Mustang
10-1488 1" bore, push rod not included

1968 F350
10-1393 1.125" bore, no pushrod

I'll keep digging, I'd like to find a drum/drum 1.25" bore.

I found 1.250" on O'Reilly's site, but its for a disk/drum setup.
10-1529 1.250" bore.

Can I remove the residual valve on the disk/drum MC and use it as drum/drum? Or is it not worth it for the extra 1/8"?

It would actually be pretty awesome if I could use the big bore mc, because eventually I will go to disk brake in the front and theoretically all I'd have to do is reinstall the residual valve.
 

bubba22349

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Yes you can change out the residual valve for a Drum / Drum unit from a rebuild kit or remove it and use an external residual valve (hot rod / street rod style). I believe that the Disk type residual valves holds about 4 pounds residual pressure and that a Drum type is 10 pounds. On converting the brake light switch all you need is a stock 1964 up Falcon brake light switch or Mustang unit should be same and the wiring harness (or rework your current wiring) then make a bracket to weld on the brake pedal assembly so that the switch is pushed in (normally off) when touching the brake pedal, you could also use a Micro Switch to do the same thing. Good luck :nod:
 

CoupeBoy

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More digging around the intarwebs..
MBM Master Cylinder FAQ -- mbmbrakeboosters.com
Question: How does a disc brake master differ from a drum brake master?
Answer: A drum brake master will differ from a disc brake master in two ways. The amount of fluid that a drum brake master has to move is less than disc brake. Drum brake masters have 10 lb residual valves at the outlet to keep a residual pressure on the drums. If you use a drum brake master for disc brakes you would move an insufficient volume of fluid and the disc brakes would drag because of the residual valves.

Question: What will happen if I use a master cylinder for drum brakes and it doesn't have a residual valve?
Answer: You will have a spongy pedal and you'll have to pump the pedal to get good brakes.

I find these next ones to be extremely interesting..
Question: I have manual brakes and I have an extremely hard pedal. Why?
Answer: Check the bore size of your master. If it is larger than 1" then you will have a very hard pedal.

Question: What bore size do you need for manual brakes?
Answer: If you use anything larger than 1" then you will have an extremely hard pedal.The smaller the bore the more pressure that is output to the wheels.

From another website..
Why Residual Valve Needed??? -- HotRodders.com
redsdad":23gxci4c said:
The residual pressure valve is necessary for drum brakes. The seal lips on the wheel cylinder cups only seal one way. The hold the pressure in the system. They will allow air to pass them into the system if the air pressure exceeds the line pressure (absolute not gauge). It can happen. If it does, you will have air in the system and a spongy pedal. A 10 psi residual pressure valve is the commonly used for firewall or under floor MC's on the drum brake circuits only.

The square cut o-rings which seal the caliper pistons on disc brakes seal both directions. So, provided the calipers are below the MC, you don't need a residual pressure valve. If the calipers are above the MC, the liquid head can cause the fluid to go back into the master cylinder, retracting the pistons, causing a low pedal the next time you hit the brakes. A 2 psi residual pressure valve is commonly used for under floor MC's on the disc circuit only.

Most MC's made for drum/drum or disc/drum have residual pressure valves built into the drum circuits in the MC, right behind the flare seal. If you are using a disc/disc MC (or a disc/drum MC on a drum/drum system), you will have to put an external residual pressure valve on the circuit which was intended to be disc but is now drum.

sounds like I have a wicked case of overthinking things.. :banghead:
 

CoupeBoy

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There are no dual reservoir master cylinders until 1967.
They may have started using brake pedal mounted brake light switches starting in 64/65..

I'll probably just take a good look at my '68 brake light switch and emulate its setup, use the same switch.

Luckily I won't have to worry about any of those pesky reverse lights that those darned new cars have.
 

aribert

Well-known member
My Falcon is (still) drum/drum. I bought a drum/drum tandem MC for a 68 Falcon/Mustang, dismantled it and drilled and tapped the end of the tandem MC for the hydraulic actuated brake light switch. I also switched over to DOT5 at the time. Dot5 and hydraulic brake light switches do not like each other. While my original bake switch was still functional when I made the brake fluid switch over, it failed within a year (I figured it was just old age). But since then all new switches also fail in less than a years time (it requires progressively harder pedal pressure to activate the switch).

I do a bulb function check every time I get ready to back the car out of the garage and am aware when the effort to activate the brake lights begins to increase. Nowadays I replace the switch before each driving season (and a few times also late in the season). All in all a bit more work than its worth to avoid some minor rewiring of the brake pedal switch.
 

thesameguy

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DOT 5 or DOT 5.1??? You should never use DOT 5 in a system not expressly designed for it as the silicone content is too high. DOT 5.1 has the same silicone limits as DOT 3 and DOT 4, but with the higher boiling points of DOT 5. Bottom line, DOT 3, 4, and 5.1 are broadly compatible, but DOT 5 is a totally different animal and cannot be mixed!
 

aribert

Well-known member
I did not mix brake fluids, I drained, flushed, rebuilt the wheel cylinders and then switched over to DOT5.
 

fx2nut

Active member
BCOWANWHEELS":2rdjdm65 said:
use 1970 c-10 chevy m/c, no porp valve needed

Why is a porp valve not needed? is there any need to change shaft or is it a plug and play?
 
a little late to the party. I'm doing this conversion as well on a 63 I'm using the 1968 Mustang drum/drum. No proportioning valve. Stock push rod. T for brake light switch on back lines. I would like to relocate a switch to the brake pedal. I saw a thread in the past that said a 80's ford pickup switch would work. Anyone have that? I'm having trouble bleeding rear units. I'm going to change the rubber lines and try again. I may crack and buy the Motive bleeder too.
 
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