Brakes - am I expecting too much

[cj847]

I have a 67 2wd. The brakes are all 100% new either by me or the previous owner. The front is a CPP disc kit, including booster and master cyl, and the rears are rebuilt drum brakes.

My issue is poor braking. The front brakes don't seem to do anything. My latest experiment was to completely disconnect the rear brakes. I drove it and it will come to a stop, but no matter how hard I push the fronts will not lock up. I can drive in reverse and slam on the brakes and the fronts will lock up. I know trucks are light in the rear end, but any type of panic push on the pedal results in immediate rear lock up. I replaced the combination valve thinking it was bad, but no change. I've bled and rebled the brakes at least 1/2 dozen times. I added a wilwood proportioning valve to the rear and have it adjusted to minimum (50% output). This makes the truck drivable. But still not good. I have had dozens of vehicles with this same gm brake set up and never felt the brakes were scary like these are. Any ideas on what's happening?