I'm rebuilding a master cylinder for a Cortina mk3 with servo. it's a first generation of 1972 model.
the cylinder doesn't have mention the bore, but only a reference with many numbers from Girling.
how can I know the bore? or how can I know where to buy a kit to rebuild the master cylinder?
thanks

Try Big Red they should be able to sort you out. Clicky Cheers Ray

It is just a tandem 13/16" (20.6mm) bore Girling tandem cylinder --- If you are using this on your build without a servo would strongly advise using a more suitable cylinder with a smaller bore otherwise you will need excessive pedal pressure to stop the car.

You might want to consider the master cylinder from a a pre 1990 VW Polo without servo. or a pre 1990 Fiat Panda

so a smaller bore helps unassisted brakes?

Pressure = force per unit area
Ergo :

Same force applied a smaller bore piston = higher hydraulic pressure.

here is the number engraved in the Girling master cylinder body (and this is all):

098 646776683 G

if this sounds anything to anybody... please tell me.

thank you
Amadeu

Thats just a casting number it is the same for all master cylinders of that general style.

so I have to desassemble it to measure the bore. thats it?