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MG MGB GT V8 Factory Originals Technical - brake master Cylinder swaps?

Has anyone tried swapping thier brake MC for a larger or (here in the US) more common domestic unit? I am faced with replacing mine and $200+ for a old special unit that I will need a proprtion valve to run with my new rear axle just does not sound appealing.

From what I found the stock MGB (76+) units are MC:13/16"bore, rear cyls:13/16" bore. I could not find data on the front calipers.

13/16th is a hard to find unit, but I think 7/8" and 15/16" units should not be too bad. I know a mustang brake MC is under $100, ad a $50 proprtion valve and you've saved $50 and gotten a more modern unit that matches the rear brakes I plan to put on..

Has anyone done something like this!?!?
Larry Embrey


I am planning on using a narrowed 9" or 8", haven't decided yet, rear under my setup when I get it all together. I also intend to have rear disc brakes. Your idea has crossed my mind as well. A modern master cylinder would be an excellent upgrade, and a lot more cheap to replace in case of failure. I haven't done any investigating on different master cylinders yet, but if we could find one with the same bolt pattern as the MGB it should be possible to make it work very easily. We may have to adjust how far the rod travels, but that shouldn't be to much of a deal to get working. I will let you know if I come up with anything. Please let me know know if you come up with anything as well.

T Johnson

For my '73 mgb conversion. I bought a mid 70's Vega MS. I'm hoping that it works okay for mine.

If you are using rear disc from a Ford, I imagine you will also change the front brakes. Then the MC to use is the one that works with the brakes you have.
Any MC with the same dia piston will work.
If you are talking of adapting to mount in the same location. It would be very hard to find one that bolts directly. The pedal box from the newer B's will be easier to adapt a MC.
I have use Wilwoods tandem MC and the single MC, they come in differnt piston sizes and are inexpensive.

Fiero, and some of the small cars have smaller (phisical size)MC that would work and perhaps simpler to install.
Bill Guzman

I use MC AP Racing CP2623, 3/4 (19.1mm) for front and 0.70" (17.8mm) a rear. I have 295mm rotor with AP Racing callipers four pots front, and 270mm rotor, two pots callipers, rear. Good braking.

Michel, what size MC are you using for your clutch.
I am in the works of installing similar MC Wilwood, I need a MC for my clucth.
David Herbert

It's a Girling MC 0.7" (17.78mm) with "big" outlet port 7/16x20 for hose dash 4. The slave cylinder is OE.

This thread was discussed between 25/03/2004 and 27/03/2004

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