Master Cylinder Mystery! or not

[bwwooster]

So... in an attempt to get more shove onto the rear brake pads, I got a master cylinder for a '94 Tempo, which has a smaller bore for the rear circuit than the front.

http://i157.photobucket.com/albums/t47/johntennyson/tempomc.jpg

However, it's also got ports on the bottom of the cylinder! I haven't seen these before.

http://i157.photobucket.com/albums/t47/johntennyson/323752_fenm1950003_1.jpg

Are these for bleeding the system? What do I do about them?

Thanks!

John

[Jeff Kleiner]

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/05/dc/16/large/0900c1528005dc16.gif

There is a seperate line for each wheel, hence 4 ports.

Jeff

[Jim Schenck]

Adding that to your brakes won't affect your front to rear bias, the rear chamber being larger helps activate drum brakes quicker so they match a front disc but once the pressure builds up it will still be even to all 4 wheels. The problem is there is no mechanical connection between the front and rear pistons, the fluid pressure from one pushes the other, therefore the pressures produced will always balance out to be the same. I thought the same thing you did and went to a ton of trouble to adapt an older Mercedes master of a similiar design and then when i figured out it didn't work I got to thinking about how they worked internally and realized the problem. Just trying to save you a bunch of trouble up front.
I also thought about using one of these: http://ecihotrodbrakes.com/brake_pressure_multiplier.html but they had quit making them at least temporarily. In the end I just adapted dual masters onto the stock pedals.

[CraigS]

Dang Jim, you really know how to bring on the rain! Ha, ha. At first I thought this could be the long sought answer to mustang brakes on an FFR. And quite simple too. Unfortunately your explanation makes perfect sense.

[bwwooster]

Yep, I did some more reading about the step bore MCs and yep, it's about pedal travel, not bias. Hmmm... back to the drawing board, so to speak...