Soft pedal after conversion.

jpl572103 said
I've got a similar low pedal problem on a 66 Dart. Right stuff disc conversion/ adjustable prop/ 15/16 master/ arms/spindles/etc. Manual brakes. 11x2 1/2" drums on the rear. Pushrod lengths were identical comparing the old single master to the new dual master. Bench bled master/ then vacuum bled each wheel. After the conversion the pedal pushes down 1/2 then gets hard. During the install I plugged the rear channel on the OE distribution block and made a new line from the master to adjustable prop then connected to the existing rear brake line to the rear wheels. I am reusing the 1/4 line connected to the new master front channel, that was connected to the OE single master to the distrubution block that is supplying fluid to the front wheels. So, the only thing that is not 3/16 line is the OE 1/4 line that is now coming from the master front channel to the distribution block which supplies fluid to the front wheels only. Shoes are adjusted/Calipers installed correct/ the only thing I can think of to do is to try replacing the 1st section of 1/4 line about 18" and make it 3/16 and see if that makes a change. Lines are connected to the master correctly.

Which master did you use, exactly?

Your front brakes should be fed from the rear reservoir (red arrow, large reservoir).
Your rear brakes (with proportioning valve) should be fed from the front reservoir (green arrow).
Running them reversed can cause two things:
-The master can run out of fluid to supply the increased volume required by the disc brakes if hooked to the small front reservoir.
-The residual valve in the front port (used in drum circuits) and lack of in the rear port (not needed for disc brakes) can cause various weird symptoms like calipers hanging up, wheel cylinders draining back, tough to bleed, etc.

And just so you know, that's 3/16 brake line, not 1/4.