Upgrading from a Single Master Cylinder to a Dual

I have a '66 TC with a single master, 4-wheel drum brakes & a 383 with a 4 barrel. I'm starting to get the car drive worthy after having sat for 16 years and came across a stock load of extra/new parts. My dad was a mechanic by trade and always stocked up on parts for his cars. Among his stash was a Cardone 10-1327 Dual Master Cylinder. I'm assuming he had planned on swapping the single for the dual, but never got to it.

I believe prior to '67 all master cylinders were of the single type and beginning in '67 due to saftey regulations cars began coming equipped with "dual master cylinders" as well as front disc brakes and 15" wheels to accomodate them.

Although the '66 already has a new single master I'm thinking of doing the switch since I have the part. I've looked at the brake system and see the brake distribution block going to the brake lines. The block has 1 input (from master) and 3 outputs; 2 for the front and 1 for the rear.

This looks like a pretty easy to do upgrade. I'm thinking all I need to do is -

1. Fill the dual master and bleed the unit
2. Remove the OUTPUT line from the current single master.
3. Remove the single master and install the dual master.
4. Connect the output line (from step 1) to the FRONT output of the dual master.
5. Remove the REAR INPUT line from the distribution block
6. Cap the distribution block
7. Install a New line to the REAR output of the dual master
8. Install a coupling between the opposite end of the New Line and the REAR input line (removed in step 2)
9. Fill the reservoir and bleed the brakes

Note: Since this is a 4-wheel drum brake system I won't need a proportioning valve unless I were to convert the front drums to discs.

So does this sound correct to you old pro's?

The more important question is whether this Cardone 10-1327 unit will work as most everything I've read on the 10-1327 is that it's for a '67-68 with a 440. But that could be because the duals came out in those years and those cars had front disc brakes. The dual master was not necessary or required at the time for a single master.

 

i think you mean a coupling not a union

 

Thanks - corrected - so will it work?

 

Master Cylinder

Did that on my 64 880 . I searched the yards to get the correct size OEM flare nuts that go in the master cylinder to give it a OEM look. I used vibration loops on the lines from the master cylinder and used coiled brake line protection on them also. I will need to look and see what the PT# on the master cylinder I used. Basically did exactly what you are doing. Make sure to use a flare plug when you cap the rear line at the distribution block .

 

yes did a similar thing when i swapped to a dual master in my chevy

 

You are correct, I did this to my 62 Ranch Wagon but I do have discs on front. I did not add a proportioning valve although I think I will eventually.

 

All dual master cyls I have worked on had proportioning valve's

You have a front input and 2 outputs, and a rear input and 1 output. It serves and prop valve AND dist block.

You always want the front to have more stopping power than the rear simply because if the rear goes first on slippery surface roundy round you go.


If your going to get into it I would just do it all at once to alieviate any future probs. Always loop the lines from the master to the prop valve as said

 

VERY NICE CLEAN WORK DAN! :2_thumbs_up_-_anima

How did you use to loop the lines?
The coil brake line protection... is that how the lines come or does it slip over the std line?

 

Sorry, I'm not following your 2nd sentence. What are you referring to?

The dual master has 2 outputs.

My distribution block has 1 input, 2 outputs (to each front drum) & 1 output for the rear drums (there's a "T" on the rear differential splitting off to each rear wheel).

 

With a dual master cylinder with drum brakes it will react as the same as the single master cylinder unless you have disc brakes. You will gain the benefit of if a brake line or wheel cylinder fails you will still have some braking not complete failure like the single. Done this to a lot of older drum brake cars.

 

This is probably one of the best things to do with any old car with a single master cylinder. As a mature driver of cars with single master cylinders I've had the pleasure of having the brakes fail due to leaking lines, hoses, or other defects.
While modern man calls the thing with a handle a PARKING BRAKE. Us older drivers know it is and was an EMERGENCY BRAKE.

 

a "newer" master cyl has 2 sections for fluid and 2 outputs, 1 for the front and 1 for the rear. one goes to the proportioning valve with 1 front input and 2 front outputs(for the front). The other goes to a second input(on the prop valve) for the rear with a single output that goes back and splits off to both rear wheels at the rear end.


It sounds to me like you want to block off one section of the master cyl and run a single line from it(the other section) to a distribution valve to run the brake system? That would defeat the purpose of the dual master.

What I am trying to say is find a 4 wheel drum brake proportioning valve,( I got one for my 56 so I can convert it off a 70 cutlass) get rid of the distribution block and do it right the first time.

 

Lines

By the way, what color paint did you use for the valve cover.... paint code?


I used this type of brake line , you can bend it by hand to almost any angle by hand.The vibration looped I made by just looping it around a socket . The armor you can get it by the foot from a lot of suppliers. Napa and a lot of parts stores sell the brake line in foot increments. The paint is Bill Hirsch

 

Ok, I understand what you're saying now. Your explanation was including the proportioning valve.

Sounds like you're mis-understanding me as well. We're both on the same page that the "new dual" master has 2-outputs (one for the front, one for the rear).

The block has 1-input (from master) and 3-outputs (2-outputs for the front, 1- output for the rear)

In my explanation I was NOT using a proportioning valve, just the block for the FRONT and connecting the REAR line directly to the masters REAR output via a coupler. I would of course need to cap the block where the REAR output line was removed.

It was my understanding that a proportioning valve was only used when front discs were used due to the closer tolerance of the disc pads to the disc as well as the much more effective mechanics of the discs (squeezing) vs drums (pushing). And like it was said you wouldn't want the rears locking up before the front.

From what I've read there are two schools of thoughts on the subject. I'm more on the school that a PV is NOT needed for 4 wheel drum brakes. One of the main reasons is because the mfg designed the front and rear drum brakes to have different size wheel cylinders which essentially acts as a proportioning valve. I do appreciate your input though and will give it much thought and do some more due diligence.

 

Thanks Dan!