after reading this thread from the tech section
http://datsun1200.com/modules/myalbum/photo.php?lid=1399

im kinda confused as what to do when fitting discs, as i have just pulled my master cylinder apart and found that it has the "disc" check valve in both fron and rear
the dics one apparently has 2 small grooves down the side of it which both of mine do

the confusing thing is that it is supposed to be a dics drum master and it still holds pressure on the front, well it did till i disconnected the front brakes as they were making it hard to push around the shed

so im wondering if it would be a good idea to remove the check valve front the front circuit as i still have rear drums? and would i remove both if i was to fit discs all round?