Five Lug Conv. - Why can't you ditch the stock PV altogether?

[lead09]

I know there are adapters and plug kits to gut the stock proportioning valve but why can we just remove it?

Could you just run the one line right off the MC and run a T off the MC for the other two lines? Is this impossible for some reason?

Why leave the stock PV in place?

 

[bubba-dough]

You only gut half of it. Thats why you have to keep it.

 

[bubba-dough]

http://mjbobbitt.home.comcast.net/mustang/mc.html

 

[lead09]

You only gut half of it. Thats why you have to keep it.

That disables the valve as he mentions. The part that is left in the valve it to keep the two circuits separate IMHO.

Looking at the diagram on this page it looks like the rear brake brake could go directly into the MC and the two front lines could use a t from the MC.

http://mjbobbitt.home.comcast.net/mustang/product.html

I would just look so much cleaner.

 

[bubba-dough]

Thats for the 3-2 port conversion. Its only an illustration about how it looks. There is a valve on the front brake side as well as for the back. The point of the pv is to adjust pressure for both the front and rear. http://mjbobbitt.home.comcast.net/mustang/mc/combination_valve_diagram.jpg

 

[Shakerhood]

Gutting it turns it into a Shuttle Valve.

 

[MikeC]

Gutting it turns it into a Shuttle Valve.

What's a shuttle valve?

 

[lead09]

Gutting it turns it into a Shuttle Valve.

But isn't the shuttle valve defeated because the fluid is no longer controlled by it? The fluid no longer has to go by the shuttle valve because it can flow through the pv cavity? Maybe the diagram isn't detail enough.

I just want to know the reasoning behind keeping it. The is no reason to proportion the front and the rear. Usualy it's full pressure to the front and proportion the pressure to the rear. Proportioning both will just reduce overall braking.

So as asked above what does the shuttle valve do? Did it function as a kind of metering valve for the drums? If yes then it's not needed anymore since it's 4 wheel disk now, right?

I've email mjbobbitt about this as well.

 

[Ozz]

Adding in the adjustable prop. valve to handle the duties of feeding fluid to the front & rear, doesn't that render the stock one useless?

 

[Mustang5L5]

What's a shuttle valve?

It isolates the main hydraulic flow from the reserve/emergency source.


These assemblies on our Mustangs are technically called combination valves since they house both the prop valve and the shuttle valve internally. Combination Valves have two functions. They control brake bias AND act as a shuttle valve in case the front or rear brakes fail. The pre-87 cars also had an electrical sensor tied onto the shuttle valve that tripped the BRAKE light in the dash if either front or rear brakes fail and the shuttle valve is activated.


When you gut the valve, you are removing the proportioning valve located in the front of the assembly and NOT touching the shuttle valve located at the rear.

So now the combination valve is strictly a shuttle valve. It will equal the pressure to all brakes AND in case the fronts or rears fail it will shut off pressure to them and allow full pressure to the remaining brakes

So in other words...KEEP IT

 

[trbkrb]

My understanding on the shuttle valve is that it is used in case of a severe leak in part of the brake system, such as a severed brake line. It will isolate the leaking part from the rest of the system and keep part of the brake system intact from a hydraulic standpoint and thus allow you to stop the vehicle. It is part of Ford's safety system for the brakes. It will keep you from draining the MC reservoir as a result of pumping brake fluid out through the cut line, which could occur if the valve is omitted.

Here is some info on generic shuttle valves: http://www.tpub.com/content/engine/14105/css/14105_102.htm

Edit: Mike and I were typing at the same time! LOL!

 

[lead09]

trbkrb and Mustang5L5 Thank you!

That answer works for me.