What do we put in its place Chris?
Why the hate for FAM7821? Is it that they fail often?
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With all the parts and rubber in them, there is more 'slack' in the system to take up and they make the brakes feel more spongy than they could be. The Valve is overly complex for the job that it does, it's big, yet the pipework isn't easy to get at. They are also non-serviceable, though if you really want to, they can be serviced to a degree. When they have issues, they can also be hard to diagnose.
There's simpler an better ways of getting the job done than to use one of these monstrosities. The other Valve that was used, though it would seem not in the UK, was the Inertia Valve, 13H7757 with the Tandem Brakes, and from a Hydraulic perspective, these are 'seen' in the system they same way a Pressure Shut Off Valve (like on the early cars) would be.
Like Retroman said in another thread, I can't be rid of them fast enough. Complete junk in my books.
you can just fit the limiter on the rear as per the single line cars, or an adjustable version.
Such as this you mean Nick?: http://www.minispare...assic/MS72.aspx
Sorry, I don't know my way around all the various setups like you do