Dual Master for Drum Brakes

[Tbird1044]

Well, I finally got the dual acting master cylinder with proportioning valve installed. Came out a pretty clean install. The brake pedal feels good and I hope to drive it around the block and see how it stops. Just wanted the security of a dual acting system. I know it will never be as good as a disc system, but it should get me by for a while. The car is not a daily driver anyways.
Nyles

[Tbird1044]

Here's a quick reply to my own post:
There seems to be differing opinions to the need for a "residual check valve" installation. Most seem to think that the residual check valves are only needed if the m/cyl is located below the level of the wheel cylinders. Others seem to think that they are necessary for drum brakes with conventional wheel cylinders. The thought is that the residual check valves will prevent any air from entering the system when the brakes are released. I went back and forth on this one, and thought I will try the system without the valves and see if I have a problem. If I do I will install them. Then I found a copy of an old ford manual for a 1967 Mustang and found that the factory manual showed "residual pressure valves" built into the master cylinder. I don't think you will find a m/cyl today with these valves built in. I know you can order them aftermarket, which shows 10 psi for drums and 2 psi for discs. Just curious if any of you techies have any input.
Nyles

[simplyconnected]

Think of it this way... What retracts your brake shoes?

We depend on good springs that are not weak from overheating. Yes, it gets mighty hot inside a drum brake and the shoes cover most of the drum's surface area when they are applied

So, springs push brake fluid back into the M/C. The rear wheel cylinders are smaller in diameter than the fronts. The brake line is longer to the rear as well.

It could be that brake engineers wanted the rear shoes to retract slower than the fronts. Remember, the original lines were all tied together into one block. Now, they are separated with unequal wheel cylinder bore sizes front-to-back.

If you use a 10 psi valve for the rears, I don't know if it will keep the shoes at the drums. If it does, that will negate self adjuster compensation because they depend on the shoes retracting in order to ratchet the star wheel. If they slow down the retract, I see no advantage in that. Properly adjusted brake shoes 'scuff' the drums, so there isn't much retract. Why restrict it?

I have not found air in my system with or without residual valves. - Dave

[Restifier52]

Looks really nice.

[RicFlairbird]

very interesting thanks, planning to do the same for a car that is a daily driver

[big bird]

where did you get the parts

like the set up but did not see what part numbers to order.Has anybody installed a modern power brake booster with duel master to a drum brake car.Thanks Ernie

[keith]

Clean looking install.

[Tbird1044]

I bought a master cylinder from local parts house that fits a 1967 Mustang, dual system, with drum/drum brakes. They offered 2 cylinders, one for power and one for manual. Both had the same bore size, but the one for manual brakes included the brake rod going to the cylinder. I read from another user that if you buy this setup, and use their rod, you need to install a spacer type bushing where the rod connects to the brake pedal. I opted for the power brake cylinder and used my existing rod. Rod length can be compensated by adjusting an eccentric where the rod connects to the brake pedal. (see maint. manual)
For the proportioning valve, I used a PV4K-2RM(RM=right mount) ($60) from MBM that states it is for a disc/disc setup. I contacted MBM and they said it will also work for a drum/drum setup. (equally proportioned) The problem is that they also supply the steel tubes from m/cyl to prop. valve. Both m/cyl and prop. valve had 1/2" and 9/16" tubing connectors, but the locations were reversed. 1/2" on m/c was at the front and the prop. valve had the 1/2" at the rear. I needed to redo the 2 small tubes using their tubing nuts.
It took a couple of trips to the parts store to get all the right tubing fittings, adapters and connectors. One I had to buy on Ebay, because I couldn't find it locally 3/16 X 1/8NPT X 3/16 TEE). Needed that to install the brake light switch. I wasn't ready to convert to a switch on the brake pedal, but this would have been a good time to do that.
A tubing bender and flaring tool are definitely needed. Some local parts stores have the tools on a loan program.
Hope this helps.
Nyles

[dgs]

Nice work. I may do this on my car. The drum brakes don't bother me too much, but the single circuit does. I assume you split the circuits front to back?

Do you have the under dash booster or manual brakes? My car has the booster in the engine compartment, do you think this master cylinder will work there? Also, did you make the proportioning valve bracket or did you buy it?

[simplyconnected]

The problem is that they also supply the steel tubes from m/cyl to prop. valve. Both m/cyl and prop. valve had 1/2" and 9/16" tubing connectors, but the locations were reversed. 1/2" on m/c was at the front and the prop. valve had the 1/2" at the rear. I needed to redo the 2 small tubes using their tubing nuts.
It took a couple of trips to the parts store to get all the right tubing fittings, adapters and connectors. One I had to buy on Ebay, because I couldn't find it locally 3/16 X 1/8NPT X 3/16 TEE)...

Rule of thumb is, the larger reservoir (if they are different sized) plumbs to the front DISK CALIPERS.

You don't have disk calipers, you have shoes. Caliper pistons never retract, they continue going out farther, and 'use' more and more brake fluid, so they need extra reservoir. Shoes retract. So, in your case Nyles, it really doesn't matter whether you use the front of the M/C (or prop valve) for front or rear brakes. The M/C piston size is identical for both sides.

I want to point out that all the lines are 3/16" tubing. Even modern (metric) lines are 3/16" tubing but the nut threads are different. Classic cars like ours use Inverted Flare Fittings (IFF) for 3/16" tubing. That tee you ordered should be called,
3/8" IFF X 1/8" NPT X 3/8" IFF for 3/16" tubing.
The 1/2" and 9/16" fittings you mentioned are also IFF for 3/16" tubing.

I always mount my devices first, and plumb to them. Like doing house wiring, you mount your boxes first, then wire to them. I've seen it done the other way and I laugh.

Forget all those benders and buy a simple pair of brake line pliers. Lisle sells them for $30 (don't ask how I know), and Harbor Freight sells them for $15. These pliers allow tight bends, right up to the nut. They work amazingly well and they fit in tight places. I won't attempt to plumb brake lines without them because they're that good. - Dave

[WoodlandHills]

Forget all those benders and buy a simple pair of brake line pliers. Lisle sells them for $30 (don't ask how I know), and Harbor Freight sells them for $15. These pliers allow tight bends, right up to the nut. They work amazingly well and they fit in tight places. I won't attempt to plumb brake lines without them because they're that good. - Dave

I want to add a ditto to this and suggest that you get the best flare tool you can. I had to design and build the brake system on my kit car and I started off using a tubing bender like I used on aircraft hydraulic systems, but quickly switched over to the pliers. I did make a few mock-ups with coat hanger wire, but mostly it was freehand. You just don't want your flares to leak after all the trouble of bending and installing your lines. Also, if you are using steel tubing you might want to paint it with something from Eastwood or POR15 to keep it looking good, it depends on how much authenticity you are going for.

[big bird]

thanks nyles tbird1044

thanks for the responce.Sounds like you put a lot of time and effort to make your tbird much safer.Well done! Ernie

[Tbird1044]

I took the car for a test drive around the neighborhood today, and a friend riding with me ask how are the brakes. I hit the brakes and almost put him through the windshield. YES, the brakes are fine.

Nyles

[Tbird1044]

I did end up buying a brake line pliers and using that for the tight bends. Worked pretty well. Just have to be careful not to crimp the tubing.
As for the master cylinder reservoirs, on mine they are equal size as I bought the master for drum/drum brakes. No problem there.
The reason I mentioned the tubing, is that MBM supplied the really nice tubing, but the fittings were mis matched for me. Not to big of a deal, but if you are looking for a bolt up, it won't work
Nyles

[simplyconnected]

Good deal, you got your brakes done and working! Let's see some pictures, Nyles.