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MG MGA - mgb brake master cyl

Has anyone converted to an mgb master cyl (non-servo)set-up? I'd like to see a few pics of the bracket, pushrods etc.

Thanks, Fred
Fred H

Fred,

Do you mean separate master cylinders like the Twin Cams have or the later MGB dual circuit type.

Dual circuit is the way to go for major safety improvements, but I have never found one short enough so you don't have to cut a hole in the firewall.

Mark.
Mark Hester

I suspect that it would be possible to fit a complete early B setup (pedals, pedal box and cylinders) but that would still only bring a split reservoir, so not much of an advance in safety.

Would it not be better to fit the later MGB system, cutting a section from the bulkhead and welding /bolting in a box on the footwell side to close it off? It would need a gasket, but if the box was made to be mounted with captive nuts, it would make any access to the banjos or rear joints a great deal easier

dominic clancy

See the Master Cylinder Blowout thread where this subject has been brought up
dominic clancy

Dominic, the mgb system from 68 - 74(i think) has a brass pressure loss switch which gives you a dual system in the event of a failure. I have the ms, brackets and switch etc, but I'm trying to see if I can get som setup ideas.

I'll reread the blowout thread

thanks, Fred

Fred H

Fred,

I do not have any experience with what you call the MGB brass pressure loss switch, but are you sure that it gives a fully dual system?
On the Triumph cars of the same period, and probably using the same parts, they have a brass switch at the junction of the front and rear brake lines. This brass switch contains a shuttle piston which moves either to the left or right, depending on whether the front or rear brake lines fail.
The piston makes an electrical contact which turns on a warning light on the dashboard. This switch does not give a truly duplicated system as it does not operate if the pressure failure is in the master cylinder, or if it is between the master cylinder and the switch.
The Triumph has a tandem (dual) master cylinder in addition to the switch.

Mick
Mick Anderson

Mick, yes that's the system. I wasn't aware that it didn't cover a ms failure, but it makes sense. I have all the mgb parts inclucing the brackets, but I'll look into the Triumph system.
Fred H

OK, I had alook at my mgb parts.
1. the ms as shown in moss as 68-741/2 has a divider in the reservoir and 2 seperate lines comming out of the ms

2. It will definitely fit without hitting the bulkhead

3. the bracket width interferes with the wiper motor

4. the mgb bracket has taller pedal pivot holes

conclusion:
1. the mgb bracket could be lowered

2. the mgb bracket could be shifted away from the wiper motor IF the top of the brake pedal were bent sideways towards the centerline of the car

I think Dick Leuning at MG Limited might already do something like this. I'll fool around with the parts I have and and I'll also check with Dick and report back.
Fred H

Fred,

If your MGB brake master cylinder has a divided fluid reservoir and two pressure lines coming from it, that is all you need for a full dual system.
The brass switch does not contribute anything to the dual operation. The only function it has is that it contains a shuttle piston that senses the difference in pressure between the separate brake lines during a hydraulic line failure and moves to one side to operate the warning light.
It is also convenient as a hydraulic line fitting for the two lines, one to the front brakes and one to the rear.
You do not need any other parts, I just mentioned Triumph as an example. If the MGB Manual does not show a cross section drawing of the switch I can send a scan from the Triumph Manual.
Is the bore of the MGB master cylinder the same as the MGA? And of course it must be the non-servo type.

Mick
Mick Anderson

This thread was discussed between 01/08/2006 and 03/08/2006

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