need help on diagnosing caliper piston retraction
 

my front disc pads are dragging too much, both sides. It's a 69 Chevelle with the stock setup. I installed new calipers but that didn't solve the problem. I greased the pins and the calipers slide good. When I bleed them, the fluid pumped through easy, and the pedal feels ok.

could the master cylinder piston cause the caliper piston to not retract?