There are several items:
1. Is the master you are using for a disc/drum? if you are using drum/drum master you need to remove residual valve in the master front line.
2. Check your rubber lines. clamp them off by the steel line with vise grips and check pedal (possible line expanding)
3. Make sure the calipers are on the right sides ( the bleeder screws should be on top )
4. The drum brake power boosters in some cases is not strong enough use a dual diaphram booster.

more info: does the pedal go to the floor? is it mushy? does it stop and them bleed down?

let us know good luck