k5 brake mystery

[N-Smooth]

it is a 87 k5, swapped in 14ff and d44 and the brakes were lacking of course. now have a brand new brake mc, for a 78 one ton and the rear brakes will lock up, but the front has no pressure. have braided stainless steel lines, so no bulging, also no leaks.
can't figure it out and it is frustrating.
could it be a problem with the prop valve or what?

thanks
nate

 

[I Lean]

Did you bench bleed the MC before install?

 

[ALF]

discs or drums in the rear? but it sounds like you just need an inline prop valve

 

[Meat_]

I had a 8 lug 10bolt and a 14bolt in my previous '87 K5, I stayed with the stock MC and it would lock up 305 x16's with a 4 horse trailer on board.... sounds like you didn't get it bled properly. On the 10bolt swap you don't even change the calipers....

 

[N-Smooth]

its a friend of mine fixing this and then i'm buying it from him.
but, he did bench bleed the mc before putting it in and he said he went through two big bottles of fluid bleeding it on the rig. he said it worked fine with the old 10 bolts, it has been since he swapped the 14ff and 44 that he is having problems.
i guess after bleeding it really good the pedal feels stiff but when you start it up the pedal just goes to the floor. is that a booster problem?
he thinks it might be the front calipers are just plain not working, but i'm not sure what could really cause that to happen.
we are going to really dive into this probably this weekend, but it is becoming very frustrating.
nate

 

[Brad J]

the pedal feels stiff but when you start it up the pedal just goes to the floor. is that a booster problem?

Yes I would say so. I also had the same original problem you're having & bench bled the heck out of a reman MC & finally deemed it DOA & exchanged it & had no more problems

 

[Shawn]

You still have air in the lines. Sometime I have to remove the calipers (with the lines still attached) and make sure the bleeder is pointed straight up. I always tap on the calipers while gravity bleeding them also. Sometimes just pumping and releasing the pressure is not the best way to bleed brakes.