Dual vs single feed master cylinder

[Track T-4]

I am in the process of going through the brake system on my T so have a few related questions. My T currently has a single-feed MC purchased from Total Performance about four (?) years ago. I've never been able to get a complete full brake pedal so am planning on a few changes. The brakes are drums on all four corners so I'm not sure if this MC was the right one since, in hindsight, it appeared Total Performance mostly leaned toward discs on front and drums or discs on the rear. So here are my questions:

1. It's my understanding a dual-feed MC is recommended over a single-feed MC because if you lose one wheel cylinder with the single-feed MC you lose all brakes. If you have a dual-feed MC and you lose a wheel cylinder how will you know? Is there a different braking feel, do you install idiot lights like on new cars, just watch for a puddle of brake fluid or...?

2. Is there a standard dual-feed MC I can purchase that will work with the four-wheel drums? How do I know which one to purchase?

3. I have 6-7/8" of space between the MC mounting plate and the trans mounted cross-member. What is the length of most dual-feed MC's and will I be able to get one that will fit in this space?

4. I am going to install a 10-pound residual valve in the rear circuit (close to the MC) since the MC is under the floor and I want to do all I can to improve the bleed. Any reason not to also install a 10-pound residual valve in the front circuit too?

Thanks in advance for your advice.
Bruce

 

[2old2fast]

Do you know what the brakes came from ? Might be able to match up a factory setup ??
dave

 

[Hotrod46]

The main reason to install residual valves in drum brakes is to prevent the return springs on the shoes from forcing the shoes back too far from the drums. This can cause you to have a lot of pedal travel before you actually get the shoes on the drums. I have 4 wheel drums on my car and I used them.

With the dual feed MC, the most important thing is to make sure you can move the piston all the way through it's stroke. Mount the dry MC in a vise, push the piston all the way to the bottom and measure the travel. Whatever that distance is, your pedal has to be able to push that far or you won't have brakes if one end fails.

You can test whether your system is actually working right by having someone crack open a bleeder on one wheel(with a bleeder hose attached of course) simulating a leak on one end of the car. If your pedal goes all the way to the floor, something isn't right. It should go farther than normal, but still build pressure on the remaining end.

One thing most people don't understand is that the brake failure switch built into most factory distribution blocks is operated by a piston that is balanced by brake pressure. If one brake circuit blows out, the piston is forced over to that side and actually helps to seal the leaking end. You sometimes have to crack a bleeder on the good side after you fix the leak to get the piston to recenter (turn the light out) or you might not get full braking on the end that was bad.

 

[fordsbyjay]

If you lose the front or back you will notice that it takes more effort to stop the vehicle because only 1/2 your brake system is working. Having lost the brakes in my 66 Fairlane in rush hour traffic using a single pot m/cyl I would highly recommend that be the first thing you change. As far as what size I just grabbed a Ford dual m/cyl and bolted it on. The bolt spacing is usually the same width or might take a smidge of file work. On my 56 with 4 wheel drums I used the m/cyl that someone had put on my 64 Falcon. No idea the size but works fine non the less.

 

[TriodeLuvr]

I think Bruce has raised a good question. The duals sold by places like Speedway have non-equal reservoirs and seem to be designed for disc/drum systems. Here's a link to a dual MC designed for non-power four-wheel drums. There are probably many others out there.

http://www.cjponyparts.com/dual-bow...power-drum-brakes-stainless-1965-1966/p/DBC2/

Jack

EDIT: Here's a link to a short discussion on the differences in master cylinders...

http://www.jalopyjournal.com/forum/showthread.php?t=622018

 

[Track T-4]

I've been told the front backing plates are '39 or '40 Ford so replaced cylinders with that make/year.



The rear end and brakes I'm not too sure about. Here is an old shot before cleanup and paint, maybe a Ford 8” or 9”? Number on it is 4J29. Anyone know what that translates to?

 

[choppedtop]

That number doesn't come up with anything. Got a picture of the front side? I suppose the tag is missing off of the pumpkin bolts. Does it have a hood over the pinion flange? If so, it probably is a 8".
Lee

 

[meangreen]

I have drum brakes all around on my roadster, too. Front are '65 Ford Econoline and rear are '75 Ford Maverick. I'm using the dual master cylinder from a 1969 Olds Cutlass that had drums all around. The local Advance Auto Parts had it in stock and it works perfectly with my system.

 

[Track T-4]

choppedtop,

Here's a photo of the front of the differential:

 

[meangreen]

That's a 9-inch Ford. The tag is missing; it would normally be hanging on the bolt that you can see peeking out under the panhard bar... Speaking of the panhard bar, it looks like the panhard bar bracket may be bent slightly - not a problem unless it flexes, but you may want to check with a measuring tape and see if the rear end is still centered.

 

[choppedtop]

Yeppers, that is a 9 incher alright. The eight inch doesn't have the little humps over the bolt holes either.

 

[Track T-4]

Thanks, Guys. The panhard bar seems okay, might be a optical.
Now to figure out which master cylinder to go with and see if it will fit in the available space. Here's a pic to give you an idea of the space I have. Might have to go with a remote electric brake switch to make it fit.

 

[meangreen]

I measured my '69 Cutlass master cylinder; it's 7 3/4 inches long (7.75") from the firewall to the tip of the casting. The brake lines come out the side instead of the end and since it was originally engineered for 4-wheel drum brakes it does not require a proportioning valve. I can post a picture of it if you need it. It looks like you might have just barely enough room.

 

[railroad]

Another master cyl option is the 1967 Ford. They still came with drums on all 4 that year. Disc were available so you will have to verify the part. Good luck,