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MG MGB GT V8 Factory Originals Technical - Single stage brake system upgrades

Hello MGB enthusiasts;

I ran across your site while searching for a master cylinder fix for my son's 67 MGB GT. I'm getting very frustrated trying to get the brakes to work properly. Possibly someone could share some insight with an MGB novice.

The car is heavily modified with an Olds 215 V8, Borg Warner 5 speed, MGC rear with Mercedes wire wheels fitted to accomodate 235/14 radial tires and misc other touches but the brakes seem to be stock, single stage type, possibly from an earlier year.

After several years of non-use by my son, I decided to use the car as a daily driver. The brakes were still functional, but the petal had about 3" of travel which I assumed to be excessive. After inspection of the components, I installed seal kits in the master cylinder and rear wheel cylinders, one of which had showed signs of leakage. I bench bleed the master cylinder, installed it, then tried to bleed the wheel cylinders using the 2 person method. The brake petal would not readily return after first being depressed, so I bleed the system using a vacuum bleeder. This worked OK, but the brakes are no better than before and still the petal doesn't fully return sometimes.

In frustration, I tried to buy a new or rebuilt single stage master cylinder but couldn't find one locally. What I would really like, especially in consideration of the power train, is to substitute a different master cylinder which would offer improved braking performance. I have some metal fabrication skills and resources.

Frustrated and confused,

There are multiple brake upgrades you can perform on your MGB. From a simple conversion to a daul system as used on 68 and latter MGBs to custom rotors and calipers.
You may want pick up a copy of, How to give your MGB V8 power, and or How to improve your MGB. These books have usefull information on brake upgrades.
You may also want to talk to Roger Parker in the UK, he has a lot of Knowledge in this area and with MGs in general. He posts on this sight from time to time and has a V8 conversion web sight as well.
If you type MGB V8 conversions for a search it should come up.
Hope this helps
bill jacobson

While my car was standard I had to rebuild the master cylinder twice once for a broken bucket and another for a broken return spring. The second time when the spring that returns the piston and bucket broke the brake pedal would not return, so if your standard brake system is having that fault I would look to see if the spring in the master cylinder is the proper length, intact etc. In the long term upgrading the brakes is essential for a V8.

Clem Spriggs


If you have a servo you may need to bleed the brakes (left calliper in UK) with engine running.



Thanks for that tip, I just fitted new brake cylinders and was having problems getting a hard pedal. I figured it was the servo but wasn't sure how to solve it!

Neil Cotty

I have found that bleeding the brakes using the traditional up and down on the brake pedal, with the motor running and using an Eezibleed kit ( as a means of replenishing the master cylinder with fluid and applying a little extra pressure ), is enough to drive the most stubborn of air bubbles through the servo.
David Daw

Paul and/or David,

Servo? There is an electrical device in the brake line but I assumed it was a sensor for a warning light. What does a servo do?

Excuse my ignorance, I don't yet have a service manual.


Over on this side of the pond we call a servo, a power brake booster (vacuum type).I believe 1976 and latter MGBs used power brakes here in the states.
bill jacobson

Glenn, I am located north of LA County, send e-mail
One of the problems with MGB's sitting for a long time is that the rubber in the brake lines separates internally, thus acting as a check valve. This could be one of the reasons why the pedal does not return, as it should, and why the pedal feels spongy and has longer pedal travel due to expanding of the brake hose.

I have experience this problem is several MGB's that had sat for a long time.

Hope to hear from you
Bill Guzman

This thread was discussed between 02/05/2001 and 03/05/2001

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