Newer ford dual mastercylinder on 40 ford brakes

[19Fordy]

Originally Posted by Pat B

I use a Monte Carlo / Chevelle master cylinder with 40 brakes on the roadster.....Works great!

Pat

Pat, What years would that be?

[Richard (EV8G)]

Originally Posted by 37fatfender

" ARE safer than single".......... Thinking ahead of my self I decided that I would install the new master, bleed the system and then recreate the problem and open the rear bleeder...guess what NO brakes........pedal to the floor. I have never gotten any satisfactory explanation as to why. I do know that my master cylinder and brake lines are checked VERY regularly.

I will try:

As V-8 Bob has posted, there must be full travel of the MC piston at or before full pedal travel. Early Ford pedal ratios are such that it takes more pedal travel for a given MC piston travel, and using a 1" MC instead of the original 1-1/16" with 40 Ford brakes requires even more MC piston travel. (It may be that the later cars that originally came with the dual/tandem MC's had a lower pedal ratio, maybe
also had power brakes, and maybe less fluid was required with the Bendix brakes -smaller wheel cylinders in front and maybe rear, like 1-1/8" and 1" or even 7/8" rears. Using the 1" dual/tandem MC with old Ford brakes will require more pedal travel than with the original 1-1/16" MC and might not be getting full MC piston travel for full pedal travel... this is easy to check and would be the place to start.
Note that excessive clearance between the push rod and the MC piston will waste pedal travel. It only needs to be about 1/16", or enough to allow the MC piston to fully return when the brake pedal is released.

Beyond that, the dual/tandem MC works kind of like this: When both ends have fluid/pressure and no air, when the brake pedal is pushed, the front piston pushes fluid to the front brakes, but also that same pressure is applied against the rear piston, which in turn pushes fluid to the rear brakes. If as in your case, there is a failure in the rear brakes, there will be a pressure drop in the fronts while the rear piston moves rearward pushing nothing, because fluid in the rear is no longer present. The rear piston has a "prong" and when the rear piston has moved all the way to the rear in the MC bore, the prong bottoms out, and after that happens, the front system can again direct fluid to the front brakes. This happens in a very short time period, BUT there is a (hopefully momentary) loss of pressure to the front brakes AND alot of pedal travel while all this takes place. Obviously, if this retro-fit setup does not provide full MC piston stroke, the rear piston will not bottom out, and therefore no front brakes will be recovered - but under normal conditions with pressure in both ends, it will work just fine... right up until there is a failure.

In the case of front failure, the front piston must travel rearward alot until a big spring is compressed and the rear piston is physically pushed to the rear, at which time the rear braking will be recovered. Again, without full stroke, there will not be enough pedal travel available to recover the rear brakes before the pedal hits the floor.

The above, pertains to a typical GM dual/tandem MC, but Ford and others I believe function about the same. As can be seen, the two systems are NOT independent at all, but are co-dependent. That is why all the pedal travel, which a typical person who has not had a previous failure with a dual/tandem MC will be surprised by and may become disoriented and panic, especially if what they were stopping for is REAL CLOSE in front of them...

The workings of a dual/tandem MC is fully explained in a Motor's Manual for the late 60's.

[CA Victoria]

I am experiencing a weak brake on my (originalish) 35 with a 39 brake setup using a new 67 ford for dual MC. Bled the MC as suggested (plugging method) and bled the rears first with the front plugged and then the rears. The pedal is firm after bleeding the rears are then soft after bleeding the fronts. (I haven't tried doing the fronts first?) I'm using a pressure bleeder. The cylinders are not new but have had kits and are not leaking. Brakes have been adjusted. When I depress the pedal after bleeding all four, the first half of the stroke is soft and then firms up after depressing about 1/2 to 2/3 of its stroke. The last time I bleed the brakes I used a qt of fluid, pretty sure the air is out......not sure what to try next? The flex lines are older but do not appear to be damaged. One comment on the MC bleeding. With both ports plugged and slowly pumping the pedal I get fluid pumping into the resivour from the chamber furtherest from the rod, the other I do not see the fluid pumping into the MC. Don't know it this is common? Maybe try a single MC?

[George G]

A mc for a 4 wheel disc brake car with no brake booster?

Originally Posted by 345 DeSoto

RICHARD (EV8G) - Of all the discussions, arguments, and BS I've seen written over the years on dual master cylinder conversions, this is probably the most informative I've read. NOW I know what the theory is, behind the practical. I've come across an NOS '67 Corvette, 1" bore, manual disc/disc master cylinder (free). I will be using it to replace the what-the -hell-EVER-it-is dual master I now have on the 32 in my Avatar. Your Post has helped me immensely with what to do, as far as bleeding the Master and installing it on the system. I've included a representative picture of the MC. BTW, what is the procedure to bleed a MC which has bleeder screws on it?...

[NYfatboy]

Originally Posted by George G

A mc for a 4 wheel disc brake car with no brake booster?

Why not, I did this to my 67 mustang back in 1980- it takes a little more pressure, but works well.

[Mart]

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Is there a commonly available drum/drum dual cylinder with a 1-1/16" bore?
I remember trying to find one some time ago, and it was difficult.
Make, model, part number would be good.

Mart.

[George G]

Originally Posted by NYfatboy

Why not, I did this to my 67 mustang back in 1980- it takes a little more pressure, but works well.

No I have no problem with it. I didn't know there was such a beast. Got a part number??

[NYfatboy]

I worked at a parts jobber, and lead parts man got me a master from a big ford truck,I think maybe an inch and an eight bore, and we took out the residual check valve. Then I put a dial down proportioning valve in line to rear, and tested and adjusted until brakes worked correctly. Sorry I dont remember the part #, but look into late 70's big ford trucks. Master bolted into mustang.Hope this helps

Originally Posted by George G

No I have no problem with it. I didn't know there was such a beast. Got a part number??

[CA Victoria]

I have re read the earlier post describing the dual MC operation. In my application with the 39 brake setup the 1970s ford MC, it would be reversed. On mine the front brakes line is plumbed to the rear most chamber (closest to the plunger). If I understand ed's post the front chamber is furtherst from the plunger, this would not let the MC function as it should???????
Also pinched off the front flex lines just above the wheel cylinders and the softness goes away...
I bought the 35 plumbed this way and don't know if it ever worked properly......
Suggestions?

[coolcoupe]

I have 47 ford and wondered if a person could hookup two orginal master cyinders side by side and hook one up for the front brakes and the other for the back brakes.You could join the the two together so they would both work off the same brake pedal. Is this possible ??

[John R]

The two master cylinder approach is feasible but tricky to set up properly. Many old sports racing cars were set up this way. Part the reason was to allow the front-rear brake balance to be changed by adjusting the linkage.

[HemiDeuce]

I have just installed a 260-4893 Wilwood 1 1/16" bore Dual Master Cylinder, with two 260-3279 Residual Check Valves in my 32 Roadster with 41 Lincoln front brakes and 2 1/4" X 11" rear Ford brakes. The pedal is nice and high and I am expecting a slightly heavier pedal that I had with the 1" Fruit Jar master cylinder that I have been running. I expect to drive it this weekend, so I'll let you know how it works out.
HemiDeuce.

[coolcoupe]

Hi John,could you tell me more about the setting up part.Might be worth a try.

[HemiDeuce]

Originally Posted by HemiDeuce

I have just installed a 260-4893 Wilwood 1 1/16" bore Dual Master Cylinder, with two 260-3279 Residual Check Valves in my 32 Roadster with 41 Lincoln front brakes and 2 1/4" X 11" rear Ford brakes. The pedal is nice and high and I am expecting a slightly heavier pedal that I had with the 1" Fruit Jar master cylinder that I have been running. I expect to drive it this weekend, so I'll let you know how it works out.
HemiDeuce.

I drove my Roadster with the new Master Cylinder today and I worked great.
The pedal was nice and high and the extra 1/16" on the bore of the Master Cylinder made a nice difference in the stopping power.
I very happy how it worked out.
HemiDeuce.

[Mart]

Can anyone help with this query?

Is there a commonly available drum/drum dual cylinder with a 1-1/16" bore?
I remember trying to find one some time ago, and it was difficult.
Make, model, part number would be good.

Mart.

[V8 Bob]

Originally Posted by Mart

Is there a commonly available drum/drum dual cylinder with a 1-1/16" bore?
I remember trying to find one some time ago, and it was difficult.
Make, model, part number would be good.

Mart.

You don't need to limit your search to drum/drum masters, as disc/drum and disc/disc masters can also be used in drum/drum setups. Residual valves (10 lb) will have to be added for the fronts, and also to the rears if not present internally inside any drum outlet ports on disc/drum masters.

I recommend using a master from a power (vacuum) application, as the push rod bores are usually deeper and are safer/easier to adapt on a custom build.

One last thing--the larger chamber, as with most disc/drum masters, is ALWAYS plumbed to the fronts.

[Richard (EV8G)]

I recommend using a master from a power (vacuum) application, as the push rod bores are usually deeper and are safer/easier to adapt on a custom build.

There is a MC that we use (7/8" bore, dual/tandem) that does not have a pushrod bore, but just a "cone-shaped" dimple. I always figured it was originally intended for use with a power booster??? When we use them, we also install a pushrod guide to keep the pushrod centered in the "cone" and prevent it from falling out, worst case...

[V8 Bob]

Originally Posted by Richard (EV8G)

I recommend using a master from a power (vacuum) application, as the push rod bores are usually deeper and are safer/easier to adapt on a custom build.

There is a MC that we use (7/8" bore, dual/tandem) that does not have a pushrod bore, but just a "cone-shaped" dimple. I always figured it was originally intended for use with a power booster??? When we use them, we also install a pushrod guide to keep the pushrod centered in the "cone" and prevent it from falling out, worst case...

Richard,
Generally, non-power masters have shallow bores because the push rods are usually fixed or restrained by special clips in the bore. Power masters have a deeper bore because the push rod cannot be restrained in the bore, or separating the master from the booster would not be possible.
As long as you have some sort of guide to prevent the push rod from falling out, using masters with shallow bores is OK, but the deeper bores on power masters just makes the job easier.

[1oldtimer]

Originally Posted by coolcoupe

I have 47 ford and wondered if a person could hookup two orginal master cyinders side by side and hook one up for the front brakes and the other for the back brakes.You could join the the two together so they would both work off the same brake pedal. Is this possible ??

they've been doing that on the HAMB with chevy truck masters and a balance bar. so i would think you could use 2 stock masters if room permitted.

[HemiDeuce]

Originally Posted by Mart

Can anyone help with this query?

Is there a commonly available drum/drum dual cylinder with a 1-1/16" bore?
I remember trying to find one some time ago, and it was difficult.
Make, model, part number would be good.

Mart.

Part Number 1050 Wagner, Eis, Raybestos etc fits 40 to 48 Fords with drum brakes and has a 1 1/16 bore.
It is not a dual master cylinder though.