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MG MGB GT V8 Factory Originals Technical - Alternative brake MC?

Next up in my conversion is the brake system. The MC is shot, and the price at Moss and other suppliers is putting me off my feed. I have two rebuild kits for the stock unit, both contain some, but not all, the parts needed. My friend who does midgets has come up with a perfect replacement master cylinder that he uses. It's from a mid-sixties Chevy Nova, and fits perfectly, and a rebuilt costs about $60. Won't fit a B, though. Has anyone used a GM MC in their MGB? Or something from one of the aftermarket suppliers like Summit or Jegs? Thanks, Bill

Bill, why won't it fit, because of the hole positions?

Jim Blackwood

I used a GM MC from a Monza. Its 7/8" if I recall.
I also changed boosters to a GM dual 7" chambered one.That booster is a bit long but it clears everything.
I have yet to drive the car w/ this setup however so I cant tell you about the feel. I increased the MC since I am using Rover SD1 4 piston calipers and the increase piston area corresponded to the larger MC.
Is your car a latter RB? If so the spacing on the GM Booster mounting will bolt up to the MG pedal box.
If yours is an older model car you could also use a GM MC by use of an adapter. Look up

Also have a look at

Hope this helps,

Mike, thanks for that link; I'll have to take a closer look later, as I'm traveling now, but will send that link home. Looks like at least some interesting tech info there. Booster? what booster; my '68 GT had the manual brakes with the dual mc. I don't plan to change to power brakes unless I feel the need, when the car runs, etc. I've upgraded the fronts by way of Mintex pads and drilled rotors, metal hoses front and back. We'll see how that works for immediate future.
Hi Jim, yes, it's the hole positions. The Midget mc mounts differently to the B, and the mounting holes in the mc are placed diagonally as opposed to vertically. Bill

That's what I thought. At one time when the MGB MC was for some reason unavailable and I could only get one for a Midget I had drilled extra holes in the bracket to accommodate it. It worked fine but when the B MC was available again I went back to that one. Still, it is an option for using that GM MC.

Jim Blackwood

If I had any spare time, I'd be working to come up with a two master cylinder solution with adjustable balance bar (so I could fine tune the bias front to back). It'd be neat to be able to easily retune brake bias after, for example, fitting new tires...

Surely someone on this board has done that already, no?

Power brakes? Yuch!

Yes Curtis, it has been done by several builders. The usual course is to take race car components and fit them to the car, and I've seen several of these. For instance Michel in France has a good example.
I built one by modifying two brake pedal assemblies and using a 1/2" hardened jackscrew for the adjuster after bending a piece of allthread by standing on the brakes.
I suppose the smaller diameter used in the race assemblies must work though or it would have been made larger.
Jim Blackwood

This thread was discussed between 26/10/2005 and 27/10/2005

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