Brake Help Requested

[chevy71super]

The brakes on my 1971 K10 have been marginal scince I rebuilt the truck three years ago. The problem only got worse when I put on 35" tires. (More rolling weight.)

The brake system consists of all new component except for the hoses and the rear brake drums. (As least they were new 3 to 5 years ago.) I decided to try new hoses first, bought Superlift braided hoses. During the brake bleeding process after installing the hoses I noticed I had good "flow" to the rear brakes, i.e. when my wife held the brake peddle down and I loosened the bleeder value a steady stream of fluid came out once the air was gone. The fluid shot up in the air 3 to 4 inches. The front brakes (disk) were a different story. It took a good while to get the air out and once I did the fluid just trickled out. Not much of a stream out of either side, barely a trickle.

The brakes work better with the new lines but still are not up to their full potential. I can't get them to lock no matter how hard I stomp the peddle.

I getting to think I have a bad master cylinder. What do you guys think? I believe I should get better flow to the front brakes. What is your experience when bleeding the brakes? Should the fluid at least clear the caliper during the bleeding process. I can barely get it to trickle out. Thanks.