Dual master cylinder

[Deuce Man]

I am in the process of plumbing a 1 inch bore dual master cylinder to a set of 40 ford drum brakes. one chamber is bigger, is there a front brake port and a rear? Do I need a residual pressure check valve anywhere? Thanks Rich

[TagMan]

If one chamber is larger than the other, then the m/c is for a disk/drum set-up and the larger chamber should be routed to the front disk brakes.......you DO have disk brakes, don't you?

If the m/c does not have internal residual pressure valves, then you should install external ones, as close to the m/c as possible. You can check the m/c to see if it has internal check valves by GENTLY inserting the blunt end of a small drill bit or a paper clip into the orfice of each port. If you feel resistance, then it has one built in to it. If no resistance is felt, then you'll need to add the valves. I believe it's 10# valve for a drum brake and 2# for discs.

[Deuce Man]

40 ford drums all around no discs! Rich

[flatjack9]

Do a search. There are several very good threads on this subject. Maybe V-8 Bob will chime in. He has this pretty well down pat.

[Junknshit]

I think he is saying the wheel cyls have dual bore size. But, I've been wrong before.

[paul2748]

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The bigger chamber is usually used for front discs. However, in a four drum configuration it shouldn't really matter.

It appears that the master is a drum/disc master based on the bigger chamber. Usually, these masters do not have residual pressure valves (usually included in the separate combo valve) so you would need two, one for the rear brakes and one for the front. 10 lb pressure valves for drum brakes.

Originally Posted by Deuce Man

I am in the process of plumbing a 1 inch bore dual master cylinder to a set of 40 ford drum brakes. one chamber is bigger, is there a front brake port and a rear? Do I need a residual pressure check valve anywhere? Thanks Rich

[quickchange34]

Get yourself a duel mustang 1967 master cyl. for drum drum . They all ready have the check valves in them.

[V8 Bob]

Originally Posted by Deuce Man

I am in the process of plumbing a 1 inch bore dual master cylinder to a set of 40 ford drum brakes. one chamber is bigger, is there a front brake port and a rear? Do I need a residual pressure check valve anywhere? Thanks Rich

Just adding to what's already been said:
Disc/drum masters are really better for drum/drum systems because the larger front brake chamber is obvious, and you always want the larger chamber to the fronts, whether disc or drum. Power disc/drum masters are the best because of deeper push rod bores on most which makes custom installations safer.
Many drum/drum masters are not 50/50, even though the chambers may look the same, and connecting the rear port to the fronts could cause a displacement problem. Also, make sure you can fully stroke the master before the pedal runs out of travel.
Your vintage brakes do need residuals, and there won't be one behind the front tube seat, as production modern discs never used residuals, but check the rear drum port for one, and add a 10 lb valve to the fronts, and, if necessary, one to the rears as mentioned previously.

[36tbird]

Even if you are running all drums now, I would plumb it with the larger chamber to the front in case you decide to upgrade to discs later.

[Deuce Man]

Sounds good guys! I ordered the residual press.. valves today will finish plumbing next week thanks Rich.

[Bassman/NZ]

I went through this same scenario. I ended up ditching the m/c which was a power disc/drum Falcon unit, and bought a new 67 Mustang (non-power drum/drum) one off evil-bay for $39. Struggled for three weeks trying to get pressure with the first one, had pressure in minutes with the Mustang.

[Rocketsled]

Is an adaptor needed to fit the Mustang M/C to a '48 Tudor?

[TJ]

You do need the adapter if you are using the stock pedal assembly. You will going from a 3 bolt mounting cylinder to a two bolt mounting cylinder.

[Newc]

Hi all; I found a 34 pu with the nicest dual drum master cyl on it. It even used the large Ford tubing for brake lines. I took it to NAPA for ID, and found it was 63-66 Cadallic! New ones were still available! Also the same master was available with left or right ports. This was 8 years ago. Newc