Water and that's WATER, not coolant, boils ONLY at sea level at 212 at so called "standard pressure." ALTITUDE affects the boiling point of either water or coolant (pressure.)
But just using 50/50 coolant already raises the boiling point to 250 AT sea level, So any added cap pressure goes up from there
A 16 pound cap AT sea level should get you more than 265 degrees F. Again, altitude will affect this, as the cap is "differential" so to speak referenced to outside pressure
