The Stovebolt Site Forums The Shop Area Engine Shop Master cylinder question.......

I have a 51 3100 that I am putting a 9" F*rd rear end in. It is disc brakes from an old Merc Wagon. I have the original calipers and new rotors. Can I use a Camaro 84-87 Master cylinder for discs with the F*rd calipers?? Is there any correlation between the master cylinder and the calipers or are the somewhat interchangalbe???

The question isn't the application it's the relitive bore sizes.
Big bore=short ped travel and more ped pressure need to stop
Small bore less ped press and more travel

Yes you can runout of travel and NOT STOP

If the given MC bore doesn't match the Application
in both bores you alter the brake ratio front/rear

I have Nissan front discs with Huck (1939) rears
and no power assist....a Mustang II master
Stops just fine

Remember you want the backs to lock JUST A SECOND before the front unloaded...if you are ever going to carry anything back there
Otherwise lock the fronts first...That's where the weight is.

Dia is important but as it related to AREA of the bore....a little bit can be a lot

I once owned a LOLA T-296 LM it had no booster four wheel discs and would pull down HARD from 160+
You just have to do the math

So to make things easy, would I be better off getting an adjustable proportioning valve for my brake system? Would that possibly give me the leeway I need to get the front and back to work together- like peas and carrots?

I am using a adjustable valve in my brake system. The truck has 73-77 Camero front disk and rear drum brakes with a Mustage 67-69 ??? manual disk mastercylinder. The Mustage II's had the wronge bore size which made the pedal to soft. With the bigger cylinder the rears would lock to easy in a 1/2 way panic stop. Full panic/slam it to the floor, they would totaly lock up and just slide along. The valve let me limit some pressure to the rears. Now they don't lock, but it takes more pressure on the pedal to get it to stop. I suppose with power assist you might not notice the extra effort.

Talk to the brake parts vendors and get there recomendations. They do this all the time. You don't have to buy they stuff! Joe

Talk to the vendors - but you don't have to buy their stuff . . . :confused:

When I get customers like that I fire them - my time is dedicated to paying customers

The kind of service a vendor can afford to give is proportional to what people are paying for it.

sswapp, the in-line proportioning valves are not to be used to correct incompatibility between the master and wheel cylinders. It is my understanding that disc/drum combos require a prop valve because your front calipers need different line pressure to initiate braking. I have one on the rear line just for heavy loads (new dual-res master cylinder w/ stock drums). Match up your hardware as Mr. Proffit advised, and the prop valve will allow you to fine tune the front/rear balance.

Check out MP Brakes web sit for everything about brakes. www.mpbrakes.com

Good link Lonnie!

Tells everything but what the pedal ratio should be

Don't ask me I forgot....If you can find a Hurst-airheart FAQ sheet it's in there

J.H.
Pedal ratio is found under brake basics section. For manual 6:1 with 1 inch master cyl. bore.
For power 4:1 with 1 1/8 inch master cyl. bore.

Don't know about post war trucks but the pre war trucks exceed that by a bunch

Thanks everyone!! That website is the real deal!! They tell all!! I believe the rotor has the same 11" dia as a GM, that means that I can use the Camaro calipers in the rear to match the front, then use an all GM Camaro disc setup all the way around. Anyway, I think I am getting closer........

Pedal ratio for the AD is 6:1