i put 4 wheel disc brakes on my 72 camaro ever thing is new the booster,vacc can,master ,prop valve ,ines,line lock,adjustable prop valve ,cross drilled slotted rotors,calipers,pads,bled system many times.it wont stopp that well it seems to not have enough clamping force,the vacc. pressure is ok coul it be week because i have 2 prop valves?lucke the har is a 4 speed or i would have crashed it.  

I have 4 wheel discs on my 68 Nova and they work awesome. I only plumbed the propotioning valve through the rear brake system and I run 1100psi to the front brakes and 800psi to the rears. I have a 1"bore dual mastercylinder and pre-bled the master before pluming was all hooked up. Bleed and re-bleed MAKE SURE ALL AIR IS out!!!