Master Cylinder swap

sixtyfive · Apr 18, 2011

Have a few questions regarding swapping out the old master cylinder and replacing it with a 2000 v6 MC. I am going from stock 4 wheel drum brakes to 4 wheel 2008 GT disc brakes.

First of all, what is the part that I circled in blue? Do I remove it?

mustangmutt · Apr 19, 2011

That is the distribution block/Proportioning valve. If you are planning on running 4wdb, you are going to want one for that application. SSBC makes a nice one that is also adjustable. Or I have also run the front brakes straight off of the MC and put an adjustable valve in the line to the rear brakes. In your case you can run a line from the MC to your line lock and put an adjustable valve to the rear.

Rusty67 · Apr 19, 2011

Doesn't the new MC use metric fiting instead of SAE ? I think you will need to redo the ends on your hardline and put metric flair nuts on there with a bubble flair instead of the SAE with the double flair.

sixtyfive · Apr 19, 2011

I purchased the proportioning valve that mustang steve sells. Since the part that I circled is also a proportioning valve I should likely remove it. I would then run from the rear bowl of the MC directly to the linelock, and the front bowl of the MC to my new proportioning valve.

The new MC does use metric fittings, it also has a larger diameter front hardline than the 3/16th inch rear line. Would I be able to use 3/16th line or would i need to run 1/4 and then convert down to 3/16th before the proportioning valve?

Also, yes I will be going 4 wheel disk.

Rusty67 · Apr 19, 2011

There should be a brass adaptor available to step you down to the proper size.

2+2GT · Apr 19, 2011

The circled part is NOT a proportioning valve. It is a divider block only.

Rusty67 · Apr 19, 2011

Thanks for posting that. I didn't way to say anything because its a big argument every time I tell people that block doesn't act as a proportioning valve....

sixtyfive · Apr 19, 2011

Thanks for the clarification, if my divider block would have been hooked up to the brake light in the cluster I might have known that I was not even using my rear brakes.

Rusty67 · Apr 19, 2011

sixtyfive said:
Thanks for the clarification, if my divider block would have been hooked up to the brake light in the cluster I might have known that I was not even using my rear brakes.

All too common. Thats why I keep telling people they don't need these things and to junk them at the first sign of trouble. A union and a t-block replace one of these no problem.

ultrastang · Apr 19, 2011

The valve illustration in the previous link is a Pressure Differential Valve. That particular valve is a for a Mustang with drum brakes at all four corners.

If the Mustang had discs front/drums rear, there would be a an add-on proportioning valve in tandem with the pressure differential valve to regulate flow to the rear drums.

In the early to mid-'70s, Ford began producing Combination Valves for vehicles that had discs front/drums rear which was all self-contained in one valve block. It had a valve spool inside to sense if there was a pressure drop between the front to rear brake circuits. If, for example, the rear brake line or hose ruptured, the drop in pressure (when the brakes were applied) would cause the valve spool to shift to the side of least hydraulic pressure --the failed side. This would cut off fluid flow to the failed side and keep from draining the MC.

The other function of the combination valve was proportioning. Discs and drums don't react at the same rate when the brake pedal is applied. The proportioning side of the valve has a spool and a spring of a given tension rate. When hydraulic force is applied, via the brake pedal, the spring will resist the hydraulic force until a predetermined amount of pressure acts against it to begin opening the valve to allow flow to the rear drums.

Additionally, if a person is using a combination valve that was designed for discs/drums but have converted to 4-wheel discs, the disc/drum combination valve can still be used, if you gut the secondary [proportioning] side of the combination valve. Simply unscrew the large cap from the end of the valve body, remove and discard the valve spool and spring, and replace the end cap with a solid end cap [one that does not have a black rubber plug in the center of the cap].

Brake systems can be plumbed without a pressure differential valve, but it does take some of the safety factor out of the brake system. Gutting the secondary side proportioning circuit does not disable the pressure differential safety feature of the valve.

Combination valve commonly found in Mavericks or Granadas, for example, designed for discs front/drums rear:

Modification to above valve's secondary side if rear drums are being replaced with rear discs:

Actual combination valve showing what proportioning pieces to remove from the valve body's secondary side:

Cap with black rubber plug on left has to be replaced with a solid cap as pictured on the right:

A manually-adjustable proportioning valve can be plumbed, inline, bewteen the valve body and rear brakes, after the secondary side has been gutted, to allow fine tuning of the brake bias front-to-rear.

coolblue65 · Apr 19, 2011

So I am switching to four wheel discs (manual) I was thinking about using the 15/16" Cobra Master cylinder and this:

This should work just fine correct? (I understand that I would be missing the safety factor Ultrastang mentioned)

sixtyfive · Apr 25, 2011

coolblue65 said:
So I am switching to four wheel discs (manual) I was thinking about using the 15/16" Cobra Master cylinder and this:

This should work just fine correct? (I understand that I would be missing the safety factor Ultrastang mentioned)

Image did not show up. Was it a picture of a prop valve?

I will feel safe enough bypassing the dif valve block as I will be installing an ebrake handle.

Master Cylinder swap

sixtyfive

Member

mustangmutt

Member

Rusty67

sixtyfive

Member

Rusty67

2+2GT

Rusty67

sixtyfive

Member

Rusty67

ultrastang

coolblue65

sixtyfive

Member

Similar threads

Master Cylinder swap

Member

Member

Member

Member

Member

Similar threads

Privacy & Transparency

Privacy & Transparency