Sounds like you've still got air in there; did you bench bleed the master before installation (if you pulled the M/C out)? Did you bleed the rear lines before doing the front?
Go to NAPA and get a "one man bleeder;" it's just a tube with a fitting on one end and a valve on the other, costs a couple bucks. Dunk the valve end in a jar with some brake fluid and screw (or press) the fitting into the bleeder. Start at the wheel farthest from the M/C and move inward; slowly pump out the old juice and keep topping the resevoir off. Do not reuse the fluid that gets pumped out, even if it looks clean. You will want some "room to move" between the shoes and drums when doing this, but the final adjustment needs to be done when the lines are free of air.
I've never had any luck with "gravity bleeding" because the M/C is mounted low in relation to the bleeders.
