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Changing from single MC to dual (3 easy questions)

1143 Views 10 Replies 7 Participants Last post by  ceccacci316
I bought a 67 dual res MC to replace the single res on my '65. I bench bled the MC and have it bolted in place. Now I have to run the lines. I see from searching some people are using a '67 style dist. block, but I'd rather keep the '65 dist block and run the line for the rear direclty to one of the ports on the MC. I've already blocked the port on the '65 dist block that goes to the rear. So my questions...

1. Does the rear line have to plumb into the front port of the MC? It appears most people do it this way, but is it actually necessary? I don't think my line will be long enough to reach to the front port.

2. The #@%& fittings for the MC... Are these a special order item or should Autozone/Advance/Napa carry something like this?

3. This valve that people keep mentioning to prevent pressure loss to one side of the MC if the other side goes out... what does it do, where does it plumb in, and where can I get one?

I think that's it (for now...). Thanks for the help! /forums/images/icons/smile.gif

1 - 11 of 11 Posts
1) Rear line must go into the front port. Your line isn't long enough. You might use a 3/16" union, with a 6"-9" line, or plug an adjustable proportioning valve in place of the union, like I did.

2) You should not have ANY problem finding the fittings at NAPA. The big "chain stores" are hit & miss when it comes to fittings, IME /forums/images/icons/wink.gif.

3) By plumbing your rear line directly into the M/C and bypassing the distribution block, you have seperated your brake system already. If you plumb an adjustable valve in, per #1, you will have complete seperation of the front/rear circuits PLUS adjustable front/rear bias.

I also kept the 65 block and plugged off the unused port for the rear line. Works great.

THIS PICTURE isn't the greatest, but maybe it will help......
gt350 clone has it right if the car has front disk. If the cat is all drum, I don't think it matters and you would not need a proprtioning valve with all drum. NAPA is the way to go for the fittings. I took my MC and line to the store and got the fittings. You may need to do a little guess work since the MC is already installed.
What Clone said is right.

The block off plug should be made for brake lines. The hardware store stuff won't work. The correct fitting has a flare fitting surface. Get the plug from the auto parts store as well.

The adjustable proportioning valve goes in the rear line. Install it now, and you are ready for disks brakes as well.
Without a "modern" distribution block (post 1967) you will still lose ALL of your brakes if your system springs a leak. The distribution block is what senses a pressure differential and shuts off one side (front or rear) allowing the good side to continue functioning.

As Mustang Steve often says when faced with the question about using an old style distribution block - unhook one line and push down hard on the brake pedal. ( - scroll about halfway down the page to the brake section.) You'll find out that even though you've plumbed the system "seperately" the fluid will still drain through the common plumbing *inside* the new dual piston master cylinder.

You need a new distribution block to make the system fail safe.

John Harvey
When hooking my 2 Chamber MC up in my 65 I reused the old distribution block. I also used a pre-bent stock brake line to the rear as-well. I straighened the last bend that puts it up into the distibution block and installed the proportioning valve under the old distribution block (and a little forward). The short little line that came with the new MC then was a perfect fit.
JSHarvey hits the nail on the head. A drum brake car needs the differential valve from a 67 later Ford DRUM brake car (if you have drum brakes). It should have a switch screwed into it for the brake failure light. I got mine at a junkyard. Get one that preferably still has some fluid in it. You can just cut the lines and take the piece with you instead of hasseling with undoing the fittings in the junked car. You can use the warning light if you want to hook it up.
I guess we disagree then. I've NEVER heard of "fluid tranferring internally" in a PROPERLY functioning dual master cylinder.

What I read on Mustang Steve's page is:

"You MUST install the combination/proportioning valve from the Maverick or other 70 & up disc brake equipped Ford product , from a Mustang to a Granada or equivalent OR you must install an adjustable proportioning valve. "

I had a rear broke hose fail 3 years ago, and never lost front brakes, so I guess I'm not convinced!!! /forums/images/icons/smile.gif
GT350Clone, I am assuming he has DRUM brakes. If he had discs I assume he'd say so. Most 65 cars had drums. Drum brake cars don't use the proportioning valve. Disc brake cars must. I see you have 4 wheel disc which is a different set-up. The MustangSteve quote is for a disc brake setup.
I am also assuming he has drum brakes. What I said above works regardless of drum/drum, disc/drum, or disc/disc....

By plumbing your rear line directly into the M/C and [color:red]bypassing the distribution block</font color=red>, you have seperated your brake system already. If you plumb an adjustable valve in, per #1, you will have complete seperation of the front/rear circuits PLUS adjustable front/rear bias.

Drum brake cars don't necessarily need the adj prop valve, but I'd plumb one in for two reasons - 1) the adjustability 2) preparation for future upgrades.
By post-1967 do you mean 1968+. Do you know if this is an item that can be obtained from a parts store or is it best to get it used or from a junk yard? I have seen a lot of post where they talk about using 1967 dist block.
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