Hi Miles,
A couple months ago I upgraded to the 15/16" master Cylinder in my 71Z.
and could not get the pedal feel where I felt safe with it. I went back and
bleed the brakes again except this time I did it this way.
I used the master cylinder bleeder kit but fit the tubing over the bleeder
screws. Then I looped each short hose back into it’s own reserve bottle
with the end below the fluid level. I opened both front and rear bleeder
screws and slowly pumped the pedal to bleed the master and fill these
loops with fluid. I did this slowly so the fluid would not aerate. I let it sit
for a few minutes then did this again, this allows any bubbles to gather
together so they come out easier.
After this was done I started to bleed out the system. I closed the rear
bleed screw on the master, but left the front one open. This will allow
pressure to bleed the rear circuit, but leaving the front open will prevent
the pressure differential switch and proportioning valve from messing with
you. Normally when you are bleeding the rear circuit the front circuit will
be fighting you and you will not get a full pedal travel while bleeding.
I bleed the both rears and then swapped the master bleeders. This time I
closed the front bleeder and opened the rear bleeder. This will prevent
the rear circuit from building pressure while you bleed the front cylinders.
Now I bleed both front cylinders. After all this I had the pedal back where
it felt safe.