The MGA With An Attitude
Dunlop MASTER CYLINDER, Removing The Piston (#1) - TC-208A

master cylinder section
Here is a drawing with some dimensions of the Dunlop brake master cylinder for the Twin Cam. The red circle is location of the output port for the Twin Cam. The light blue circle is location of the output port on a slightly odd part, garnered from an eBay ad (see next page). If you need to use a grease gun to force the piston out, you need to plug the internal port between the pressure chamber and reservoir. Klaus Junker suggests a small plug of hardwood backed up by a wedge as shown in the left end of this drawing.
master cylinder pencil sharpener
Mark Hester used a plastic coat hanger with the end sharpened in a pencil sharpener. Perhaps a golf tee could serve the same purpose.
The Zerk fitting shown here is tapped and screwed into the end of a brake line flare nut fitting. A 3/8-24-UNF bolt with an axial drilled hole works as well.
zerk fitting
Addendum November 2010:
On 11/18/2010, Frank Netterberg wrote:
"My Dunlop cylinder has a plastic strap (now pink in colour) around the cylinder marked VBO 4843 MOD KIT on it. I understand that this is the Dunlop part no. for the later kit incorporating the double seal piston and stronger spring listed as BMC part no. 8G8219 and, apparently as PBR K7167x (seals only?).

"The whole assembly looks very similar to that used on a Toyota Hilux, but I have not tried it".

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