Need help with brake prob after 1 ton swap...

[coloradoblazers]

I have an 87 k5. I just swapped in a dana 60/ 14bolt from a 79 k30. Every time I try to bleed the brakes, they go soft again after a minuit or two. I replaced one of the wheel cylinders, some brake lines, fittings, and other things, and can find any leaks. What do I do now? Going to put the rear up on ramps and bleed it, let physics aid me, but I don't know what else I can do. After the swap, is the pedal supposed to be mushy, If I can get them to hold pressure,I might take it to be vaccuem bled, but i don't want any one but me touching it, so please help!!
Thanks, JAke

 

[BorregoK5]

Sometimes a change in the capacity of the braking system can place the seals in the master cylender in areas which it hadn't traveled before. If the seals were already old or travel into a corroded area they will leak. Swapping to the higher capacity braking system might have pushed it over the edge.

 

[florida4x4]

I had to bench bleed the MC to get all the air our. You might want to build a pressure bleeder system from a insecticide sprayer or have it done professionally/