Rear Disc Conversion (What Master Cylinder?)

[Boss.Hoss.Ross]

I just put an 8.8 with discs in my car and I was wondering if anyone has done a similar swap, what do I need to change (M/C, combination valve, etc.) to make the rear brakes work properly. I know discs need more volume than drums do, and the rear brake resivoir is about 1/3 the size of the front brake resivoir.

I have Discs up front and power brakes. just converted from drums to discs in rear, just to clarify.

Thanks for any help!

Adam

 

[68keyblr]

*subscribing*

 

[ratio411]

I would use a proportioning valve for a 4 wheel disc car.
Either that or an aftermarket adjustable one... they are inexpensive.

I don't think the resevior size has anything to do with it.
It all comes down to the proportion of total flow that you do or don't want going to each pair of brakes (frt vs rear).

Dave

Edit:
Check into a Versillies proportioning block, or use the block off a 4 disc Crown Vic/Exploder/Mountaineer/etc...
The later ones though, are probably metric, so you would have to custom make some lines.

 

[Boss.Hoss.Ross]

Thanks for the info Ratio11, but now I am wondering: does anyone know if I have to pull a residual valve out of my stock master? I've read something about these valves that are installed in disc/drum masters that keep the rear slave cylinders from retracting too much??

Anyone know?!

 

[Soaring1]

brake

If you have a dual reservoir MC you don't have a residual valve. Normally called a check valve on a single bowl MC. So, what are you worrying about?

 

[Pbum5]

The best Bang for the Buck MC for 4-wheel disk is the 84 SVO Aluminum MC. You can get it for under $30 rebuilt. That’s what I used on my car when I swapped to 4 wheel discs.
It's light and does the job. You have to make new brake lines because the outlets are on the "wrong" side. Get a Adjustable prop valve and you are good to go. SSBC makes a cool combo distribution and prop valve in one if you want to clean things up a bit.

 

[C6AE]

I used an '86 SVO MC (on a Fox 2.3 booster) in my 66 vert. it's a steel one. It works very well and using a Versailles dist block, I didn't need a prop valve.
The only thing I didn't like is the ports are on the wrong side.

 

[ratio411]

The 4 wheel disc Exploders have the lines on the correct side.
Otherwise they are identical to the Stang master.

 

[1320stang]

You need a disc/disc master cylinder, not a disc/drum master cylinder if that's what you had. Beyond that, Pbum, C6AE and Ratio offer sage advice. My '03 Sporttrac has 4 wheel disc as well.

 

[bnickel]

IIRC, the granada mc has the ports on the same side as the SVO mc


edit: nope, just checked and the granada has the ports on the other side of the mc from the SVO unit, so you will need to make new lines to use the SVO mc.

 

[67 Evil Eleanor]

Volume is very important. As the disc pistons are several times larger than the drum cylinders pistons, as the pads wear it is possable to run out of fluid, even faster if you have multi pistons. Then guess what, they notta work. Select one with large bowls, if yu don't needa de extree fluid, it ain'ta gona hurt.

 

[speed1972]

I would use the adjustable proportioning valve... it gives you infinite ratio adjustment

 

[BB1966]

I used a V-8 Fox booster with a 94/95 Mustang master and a adjustable valve.

 

[ultrastang]

A Drum/drum dual reservoir MC will have an RPV (Residual Pressure Valve) installed in both ports. A disc/drum dual reservoir MC will have one RPV in the secondary side port feeding the rear (drum) brakes.

A 4-wheel disc MC will not have any RPVs installed in the MC. If you use a Disc/drum MC on an all-wheel disc setup, the rear discs will drag, causing excessive heat build up and accelerated pad and rotor wear.

I've used two different Ford 4-wheel disc MCs with some disc brake conversions I've done. Here are a couple of examples:

1. Granada disc/drum MC on the left. Lincoln Mk VII/Mustang SVO MC on right; http://www.ultrastang.com/Images/Scanned/June2002/11.jpg

2. Mk VII aluminum 4-wheel disc MC I installed on a 2.3L Fox Mustang brake booster in a '65 coupe; http://www.ultrastang.com/Images/Scanned/June2002/01.jpg


3. SN-95 V6 Mustang 4-wheel disc MC I installed on a 2.3L Fox Mustang brake booster in a '65 fastback; http://img458.imageshack.us/img458/899/65053fd2.jpg

At the time I installed the SN-95 V6 MC in the fastback (2004), I couldn't locate the correct bubble flare fittings to make a direct connection to the MC's ports, so I had to use bubble flare-to-SAE inverted flare port adapters. However, since that time, I located a supplier that I can get the correct ISO bubble flare fittings from to eliminate the adapters in between.

A sample piece of 3/16" brake line I was playing around with: (ISO metric bubble flare fitting on the left end, and a 7/16"-24 SAE inverted flare fitting on the right end of the tube); http://img443.imageshack.us/img443/6972/isobubbleflare003rx0.jpg

--Steve


www.ultrastang.com

 

[Boss.Hoss.Ross]

Thanks for all the info, guys!

BTW, I have been driving on the stock braking system by just hooking in the 8.8's rubber hose to the existing system without problems for a couple hundred miles so far. If i really nail the brakes hard, the rears will lock before the fronts, but i've only tested it once and under normal conditions its fine.

I'm planning on getting put together right soon, though, so i don't run into problems down the road.

 

[Rusty67]

If you have a dual reservoir MC you don't have a residual valve. Normally called a check valve on a single bowl MC. So, what are you worrying about?

This is not exactly true. There are dual resivior MCs that have residual valves in them.

I also recomend the SVO MC. Do you have power brakes or manual ?

 

[Boss.Hoss.Ross]

I also recomend the SVO MC. Do you have power brakes or manual?

Rusty, I do have power brakes. I have stock 78 granada disc brake components up front along with stock disc/drum m/c, booster, dist. block, etc.

Like I said, the way it is set up now, I just pulled the old drum brake rear, and slapped in my disc rear and hooked up the rubber line to the axle. It doesn't stop bad at all, i'm pretty happy with the pedal, and although the rears deff. lock before the fronts under really hard braking, i've never needed to stop that fast so it's not noticeable under normal driving. Obviously I would still like it to be right, however.

Thanks for all the help guys!

Adam

 

[Jimmys66]

I did the cobra swap front and back on my 66. I used the cobra mc after a talk with a tech from Baer brakes. He admitted to me that the mc from their kit was a factory mustang piece.

I did install a 2lbs residual after my prop valve though.....

Was that a no-no? it doesn't seem to drag.

 

[Rusty67]

Obviously I would still like it to be right, however.

If you want it to be right, you need to remove the residual pressure valve from the system. I don't know if the MC you are using has an internal pressure valve or if there is one plumbed into the lines some where but if it is in the MC then you need to switch out the MC. I strongly recomend the SVO MC because it has a HUGE fluid capacity, giant bore size and it is aluminum so it is light weight and won't corrode. Since you already have power breaks you should have nothing to worry about.

I did install a 2lbs residual after my prop valve though.....

Was that a no-no? it doesn't seem to drag.

The only reason you need a 2lb residual pressure valve in a disc circuit is if the MC is lower then the calipers. This prevents the fluid from flowing back into the MC. Drum brake residual pressure valves are 10lbs and are neccessary in all drum brake circuits in order to keep the shoes from retracting too far.

If your MC is in the stock location you should NOT have the 2lb residual pressure valve installed.... unless your calipers have been relocated above your hood

 

[Jimmys66]

The only reason you need a 2lb residual pressure valve in a disc circuit is if the MC is lower then the calipers. This prevents the fluid from flowing back into the MC. Drum brake residual pressure valves are 10lbs and are neccessary in all drum brake circuits in order to keep the shoes from retracting too far.

If your MC is in the stock location you should NOT have the 2lb residual pressure valve installed.... unless your calipers have been relocated above your hood [/QUOTE]


I have had the brakes over the MC twice as a matter a fact. The friction of the roof is a poor braking material.

Seems like when I did it someone recommended the 2 pounder. I'll have to back and look.

You thinkin' I'm dragin' some rear brake?