1966 911 Brake Bleeding Problems

I have a 66 911 that I have rebuilt all of the calipers replaced all of the rubber portions of the lines and changes the master cylinder 3 times. I have hand bled, used a mityvac, and also used a power bleeder and can not get significant brake pedal.....what have I done wrong.

You may have a tiny pinhole in one of your metal brake lines , after you pump the brakes to bleed each caliper watch the fluid coming out on the bleeder screw on the caliper when released, their should be a strong steady stream of fluid from each caliper.

Sometimes when replacing brake components it is difficult to get the air out as large pockets get caught in high points of the hydrolic lines, I use an oil can with a rubber hose attached to the bleed nipple, fill this with hydrolic fluid and pump it back up the brake or clutch line, the air wants to go up so this usually works, watch the reservoir for overflow.