Z height increase

Hi fellow 3D ,ers, I have a German Rep Rap V Protos build platform X 205mm Y 210mm Z 140 , and thats my Problem Z axis I Need at least 160mm ,it is possible mechanicaly just Need to lengthen the X stop metal bracket to clear the Z movement going further than the G code 140mm .But how ?? I have been told it can be done , but not up till now how ! There is no physical stop on the Z axis to move higher so anybody out there know how to fix the Problem . Thank you Harry

If you manually move the Z axis up and it just stops at 140 it probably firmware

eg in marlin it might have.
#define Z_MAX_POS 140

I don’t think there is any gcode that can over ride this

But you can test this theory
home your Z axis, I presume it homes to Z0
move the Z up 20mm
send a G92 Z0 (ie lie to the printer that its back at Z0)
now tell it to go up 140. It should go physically all the way to 160, and stop.
Not very useful, but proves there is a 140 limit in firmware