bleeding brakes,you need two people to do this ,if you want it done right the first time,first of all everytime you hear air come out of the brake bleeder refill the master cylinder,i have not tryed gravity but i have heard of it,the way i always have done this is ,start from the farthest wheel and work to the closest to your master,i always jack the wheel up i'm working on but i am safe when doing this at the rear of the vehicle i put a concrete block and a 1 by 6 on top of the block and i take the wheel off to make sure the brake shoes are working correctly.have your buddy pump the pedal 6-7 times each time and hold them until they go to the floor make shure they go to the floor on each wheel.after you have bled every wheel just bleed the master to make sure you got all the air out and if this don't work then you got other problems,mark 1966 swbss