I have a 77 280Z that has been extensively modified. A problem with the rear alignment lead to the car sitting in the shop for an extended period of time. That problem has been addressed and I was ready to put it back on the street. However, the brakes failed to hold pressure.

Here is the status of the system.
There are no fluid leaks.
The master cylinder has been replaced.
There is no air in the system at the master cylinder or any of the wheel cylinders.

The system has been bleed but still will not hold pressure. Any suggestions or ideas will he helpful.

Welcome to NICO!

When was the last time the brake fluid was changed completely? How are the rubber brake lines going to the calipers? My first thought was that it either needs to be bled or that the master cylinder is bad, but seems like you're pretty sure that's not the case.

Could be a bad master, I had one reman unit completely missing one fo the seals, and had a new unit that due to poor machining looks like one of the seals was damaged during assembly.