No brakes

[daytona71]

Hi all. 1973 Charger disc front, rear drum. New master cylinder, new front calipers, new distribution valve. No leaks anywhere. Brake pedal slowly goes to floor. Booster push rod extends when pedal is pushed, lots of force. Blocking off ports on master, pedal doesnt go to floor. Have gravity and forced bled the lines. Any ideas what I am missing?
Thanks for your input

 

[coronet68mx]

The o' rings from the piston inside the master cylinder are old, cracked or worn out specialy if the master cylinder was too much time without use, they just can't hold the pressure from the pedal, even new they fail, no air in the lines no old parts except for that particular rubber ring

 

[coronet68mx]

You can see it here as "seals"

 

[69L48Z27]

If you blocked off the MC and pedal is solid that means the MC should be fine.

Make sure you have the rear drums adjusted up. It sounds like you don’t have all the air out of the system.