Master Cylinder with Servo Conversion

[Andysdad]

I am in the process of fitting a new Master Cylinder with a Servo. I know I have to remove the "Top Hat" but am confused as to which is the actual item. I assume that it is the item shown as "Valve Body" on the attached diagram. Mainly because it looks like a top hat . I am confused as I have seen references to and even seen highlighted the "Valve Cup" from the same diagram.
Can some one please confirm the correct item.

Many thanks[frame][/frame]

[simmitc]

It's the "valve cup" in that diagram. You should remove it if fitting discs, but leave it in place with drums on all four wheels. Removing it relates to the use of discs, not the servo per sae. The dup is rubber, the body is metal. If fitting a remote reservoir (needed with discs, convenient for drums) then you need to fit a filler cap without a vent hole.

[Andysdad]

Simmitc. Thanks for your reply. I am aware of the other elements as my car has discs fitted already just no servo. I was and to a degree still am confused by the term "top hat". There are dozens of references on here to "remove the top hat" when it looks as if I have to remove the valve cup which sits inside the top hat. Unless of course some people just remove the valve body(top hat) with the valve cup inside.
Will be rebuilding and installing the m/c today...minus the valve cup.
Thanks again.

[IslipMinor]

It is the 'seal', which is the 'Valve cup', that needs to be removed with disc brakes, the 'Valve body' should remain in place.

From the BMC Manual - the valve cup is there so that 'a small pressure of approximately 8 lb/sq. in. is maintained in the pipe-lines to ensure that the cups of the wheel cylinders are kept expanded'. With disc brakes this residual pressure is enough to keep the pads in light contact with the disc, which generates a lot of heat and wears them out prematurely. That is why it needs to be removed!

For clarity:
[frame][/frame]