[RichardJ]

Did the new master have the shallow hole needed for a P-booster? The pin on the booster needs to be checked for proper length.


Assuming the master is correct and the booster pin is checked for correct length;

Boosters are designed to hold enough vacuum for three applications of the brake pedal if the engine should die.
With engine OFF, apply the brakes 3-4 times and you should have a high firm pedal.
While holding the brake pedal down, start the engine. Pedal should drop as engine vacuum builds.