Where to start? I read and read and read the search results for brake issues now I'm just gonna ask for help. This is on a 76 K5- I did the 14 bolt disc swap while the truck was 3/4 ton. Used all factory brake stuff, just put on 3/4 ton calipers and rotors on the back. Never had good brakes during that time- Drove it very little. Fronts seems to grab while the rears did little grabbing. Now I just put the 60 up front, I also gutted the factory prop vavle (front and rear half of it). Plumbed in a Wildwood adjustable prop valve in the rear line only. I had a leak in the rear half of the factory prop valve so I just by passed it completly. So now I have the fronts running into a gutted factory valve to give me 100% pressure there and an adjustible prop valve in the rear, mounted right off the mc. I made a low pressure power bleeder. Hooked it up to the mc and opened the rear bleeders, nothing! I never worked the peddle while it was under pressure. Gave it a few more pumps and then the fluid started gushing outta the mc cover I adapted for the power bleeder. I tried gravity bleeding the system for about 2 hours last night and could not get fluid out of the rear calipers. Without the power bleeder hooked up, if I mashed the peddle some would squirt out but couldn't get it to constantly flow likeit should being gravity bled. Any words of wisdom for me? All my brake lines are SS.