Calling all brake experts!

I'm runnin Crown Vic police/taxi front brakes, and stock 64 F100 rear drums. I have 3/16" brake line with 3/8" standard fittings. I'm using a pedal assembly from a 94' Mustang GT. Stock stang MC is 1 1/16" bore, crown vic MC is 1". Currently none of this stuff is hooked up together.

My question is...... is there a disc/drum MC I can use that has 3/8" fittings that will work with my setup? I'm planning on using a 10lb residual valve for the rear, prop valve, and metering valve but want to keep everything simple.... standard flares, fittings, etc. Also, I'm going to use the mustang booster.

I was thinking 68' mustang MC or possibly this:

MC390387P $119.95
Use for disc/drum
Outlets: A3/8-24 B 3/8-24
Bore size: 1” Ports:right
Shallow piston hole power brakes

I'm at a loss.... not sure what has a similar stroke, if that's necessary, etc. 3/16" line ok if crown vic used 1/4". 1" bore vs. 1 1/16" bore effect pedal too much? effect on disc/drum setup, etc. I have decent pedal travel, but its a little less then in the stock mustang.

Let me know what you think, brakes are one thing I would never take a shortcut on.... not that I would on anything else, but you catch my drift... just want some other opinions/advice before I pick something up and wind up with less then stellar results. thanks

 

I would suggest using the pedal/booster/master from the Crown Vic, as this will ensure adequate fluid volume for the large front discs, prevent any master/booster/push rod clearance issues or mis-match, and probably shorter overall pedal travel than the Mustang, but you HAVE to check to make sure the pedal bottoms out the master BEFORE it hits the floor! Also, disc/disc masters work just fine with disc/drum systems, just use a 10 lb residual to the rear drum axle as you planned.

I have never seen a production disc/disc or disc/drum master with the same outlet port sizes. Reason? You don't want to be able to switch the brake circuits. Maybe some aftermarket masters have them, but not OEM masters. There are several "special" tube nuts available, SAE and metric, that have a 3/16" ID with several OD and thread diameters, just as the OEM used. A simple way around metric fittings is to buy a pre-made metric bubble flair tube, cut and re-flare the other end to SAE using the common 3/8"x24 nuts and unions, as the smaller metric tube size is the same as 3/16" US tube.

The Crown Vic and several other late model vehicles use 1/4" lines because of ABS and traction-control feed back to the master, but 3/16" tube is all you need on normal car/light truck brake systems.

To keep it simple, forget the metering valve, especially on a pickup, but do use an adjustable prop valve, not a "fixed" one part of a combo valve. IMO
Bob

 

Master Cylinders need adapter fittings. dont use 3/16 line back to the hose for the drums. use 1/4 inch. 3/16 is fine for the fronts, they move less fluid than the wheel cylinders for the rear. get a 5lb valve for the front and a 10 lb valve for the rear. use the mc for the mustang booster/pedal assembly. then you dont have to worry about pushrod length.

 

thanks gents! that definitely helps a lot and makes me feel more at ease.... just got a few more Q's if you don't mind. I think the stock replacement SS line I got is all 3/16" unless there's 1/4" to the rear hose and I didn't realize it...is it really an issue to use 3/16" to the back? That's what I was figuring about the 1/4" to the front (anti-lock, etc.) thanks. I'm going to have to stick with the Mustang pedal assembly/booster - long story but everythings designed around it and the pedal assembly includes the clutch, etc. so that's not going anywhere. Originally I was told the police CV brakes were the same as the cobra so I thought it would be a good fit. I'm assuming the extra 1/16" of bore on the mustang master is because the pedal ratio is less/greater, not sure but hopefully it won't matter too much with the CV brakes. I don't need the brakes to "feel" perfect, I just need them to work. I need to look at the pedal throw again, I think I only have about 4" to the floor... how can I make sure it is bottoming out the MC?

I was just hoping another MC would bolt up if it had the same pushrod length and I could avoid the metric - standard thing. I've flared brake line before but wanted to avoid it.... and it seems most aftermarket prop and resid valves are standard thread sizes. The pushrod on my booster looks like it has an acorn nut on the threaded rod that is adjustable and I have two MCs in the shop - one is the 94 Mustang and the other a 94 F-150, and the pushrod cavity seems to be the same size on both.... the aftermarket MC I listed above comes in both shallow (for booster) and regular (for manual) .... is there more to it? I have a friend with a 68 Mustang MC, if it appears to have the same pushrod cavity size, wouldn't it be fine? The other reason I'd like to avoid the Mustang and CV MCs is because they are extremely angled because of the difference in my firewall and so one of the chambers would hold less fluid. See link to pic below:

http://i637.photobucket.com/albums/uu93/nr5150/photo-1.jpg

Sorry to be such a PITA, but short of getting a degree in engineering, I don't know where else to turn.

 

friggin"A",
There is NO reason to use anything but 3/16" brake tube on any car or light truck custom brake system.

Using the Mustang pedal is fine as long as you can adjust the booster push rod for .040"-.050" clearance to the master primary piston. Do this with full vacuum (20 "HG) applied to the booster and the pedal fully retracted. I understand why you want to use a conventional "level" master cylinder, but I would stay with an 1 1/16" Mustang bore size to keep the pedal travel down.

To check for full master travel, bleed the vacuum assist, open both the primary and secondary ports, or a front and rear bleeder, and stroke the pedal. The pedal HAS to stop before it hits the floor, with force applied to the it. If it doesn't, do what ever is necessary to correct the problem, or you will not have the full benfit of a dual master cylinder, and will never have a good bleed when using the pedal method. Any/all masters have to be able to have FULL stroke capability without pedal or bracket limitations.

You are correct in that some power master cylinder primary piston push rod bores are shallow, while some manual masters usually have deeper bores.

All of the aftermarket residuals and adjustable prop valves I have or have seen have 1/8" pipe ports. A simple brass adapter, found in the fitting cabinet at your local parts store, is 1/8" pipe on one end and 3/8"x24 inverted flare ( or 37 degree AN) on the other, and solves the hookup.
Bob