Mk2: Brake pressure regulator at master cylinder?

[chopperoli]

My 1982 has an unusual type of brake pressure regulator below the master cylinder.

What's the lowdown on this part? Why is it needed with rear drum brakes? I've never seen one before, and I don't think the later models had them either- was it swapped to a valve on the rear-axle?

It is item 1 in the first pic:

[Nate]

It's to make sure the front locks up before the rear under heavy braking, which makes it harder to spin the car. Without it, the rears would lock first, and if you weren't going in a dead straight line, you'd soon be pointing backwards.

Lots of cars will have a valve attached to the rear axle instead, which can increase the braking on the rear as you pile more weight into the car (more weight on rear wheels = harder to lock up)

[chopperoli]

Thanks yeah I understood that is how they work, are there any other components different between Mk1/Mk2 brakes?

Does every Mk2 have this valve fitted on the master-cylinder then? School me ;)

[Nate]

i think some of the earlier cars had the valves fitted at the wheel cylinder instead of master cylinder. other than that, and the mk1 using stupid pressure switches on the m/c for the brake lights, i think the systems are basically the same. except fot the very early mk1s that is, which had a completely different arangement at the rear end