I have a 1986 f250 with a 73 429 in it. I'm have problems with my breaks. There's not a lot of peddle and I don't think there is any back breaks at all. The peddle goes way Down before the breaks start to grab and is slow to come back up. I have bleed the breaks and even check the vacuum its at about 17 lbs. And I don't know what I should do next

 

Have you took the wheels off to look at them, Might not have any pads on front, and the back might be just bad.

 

I check them every time I change my wheels and tires. There are still lots of pads on the front and the shoes are good on back. There arnt any leaks. I'm not loading fluid. Could.this be from the previous own leaving the calipers hang when he changed the breaks last time

 

you could have a bad master cylinder, Brakes with good pads and shoes won't go all the way to the bottom of the pedal unless there is air in the lines or a bad master cylinder. its easy enough to change one out.

 

It's possible that its a bad MC I had the same problem in my 85 I had low pressure and she would do burnout way to easily mine had low pressure and would rise slowly I had no leaks or anything what I did was just adjust the rear and I rebled all the lines it fixed it for me good luck

 

I've got a 82 f150. Think they would change out?

 

Just go get a new MC, only $16 for a rebuilt or $32 for a new one at Autozone. (Core charge $8)
Just got done replacing my MC 2nd time. For me the brake would stop OK, but then the pedal would slowly sink down to the floor, then the dash brake warning light would come on. Gradually got worse and worse over about a month or so.
A few years ago my MC went out all of a sudden one stop light it worked OK next stoplight no brakes at all.
Don't forget to bench bleed the MC.

Another possibility is the proportioning valve.

 

Here's a couple of thoughts,

1. Check the clearance between master cylinder and the booster push rod, there needs to be just a little clearance, like about 1/16. Too much clearance is wasted pedal travel. No clearance, the master cylinder won't alow the brake fluid to return to reservoir causing low pedal and dragging brakes.

2. Adjust the rear brakes up to allow about 1/2 turn of wheel (drag).