Brake plumbing question

[Dan B.]

I'm working on my fox'T-bird for a winter project. It's already got a Turbo Coupe disc brake rear. By using the TC prop valve and stock MC I've not been able to get any brakes on the back. The common solution I've read about is to swap the stock MC for a '93 Cobra unit. I'm not exactly a brake plumbing guru so please provide input!!

The '93 Cobra MC I plan on using will only have two ports so I have a couple options. Since I'm going to be completely redoing the braking system, I was just going to run a two line system from the Cobra MC and not adapt back to the three lines.

The plan is to take a single line from the port that feeds the front brakes, install a line lock and split after the line lock it to go to both front wheels. Then run the back port line through an adjustable prop valve then the entire way back to the rear.

This would eliminate the stock prop valve and the whole deal with having to gut it and get a plug. Either way I still need to get an adjustable prop valve. Retaining the stock pv would just mean the adjustable pv would go after the stock one. I'd rather simplify the system and make it cleaner.

Your thoughts??

[Martin0660]

This is sort of how my Capri is only different :D Mine has all SVO brakes (bigger in rear), but what mine does is SVO master cylinder with two lines to SVO proportioing valve ... the original set up off my prop valve was two lines to the front wheels, what I have is one port plugged, and the other to a line lock. I have a line lock with one "in", and two "outs" (common) so I have an outlet to each front wheel, and the proportioning valve to the rear brakes.

It works very well with the SVO bits, so I ddint need to do the gut and manual proportion valve deal ... I was able to do all of this right in and around the master cylinder with a few adapters (early fox BS with mixed SAE and Metric) and keep mostly the stock brake lines.

Where are you going to put your brake pressure switch with your scheme?

[Dan B.]

Where are you going to put your brake pressure switch with your scheme?

Pressure switch??

[Martin0660]

Yeah, the safety switch that turns on the "brake" warning light if something is up ;) Little round electical connector on prop valve.

[Dan B.]

DOH! Hadn't thought of that. That's why I ask questions.

My prop valve is a Turbo Coupe model.....which end feeds to the plug? Could I bypass the front brake circuit of the prop valve (to a line lock) and run through the rear brake end to keep the plug active? If I read your circuit correctly then this sounds like what you did?

Details, details, details...........

[Martin0660]

Not sure unsing the TC prop valve (for Teve's system) is a good option.

I do not bypass the prop valve ... both master cylinder lines go to the prop valve (front and rear) but I only use one out of both, then make the front split at the line lock.

I "think" if you only take one circuit to the prop valve, you are going to have to gut it ... I'm far from understanding the details, but I "think" the prop valves needs fluid to both sides to function.

[Dan B.]

Ah-ha. Then that makes sense as to why most folks retain it as a gutted PV to simply pass fluid through for the pressure switch. Never heard the pressure switch mentioned in any searching I had done before. Thanks!

Another thing to ponder.....I wonder if by eliminating the "third" MC port with a plug, converting to a two line set up essentially going to a set up like yours allow me to keep the stock T-bird MC.

[Martin0660]

I think the issue there is you wont have enough of "bore" in the MC to feed those rear discs. So many ways this all is done, but typically people end up with bigger bore MC's when doing the TC rear disc ... either the Cobra like you have or the Lincoln / SVO unit.

[Dan B.]

That's what I thought.....but had to propose the idea.

Any advise on the best place to source a Cobra MC? Looked on LMR...they have them for $90. I'm not sure which Lincoln MC would be required.

Greatly appreciate your input.

[Tony71502]

I got my booster from Ford.