From what I remember your car has about 20k miles on it and you used the Haibeck method to refill the coolant. 230’ is a bit on the high side especially if ambient temps are not excessive.
I would first do another coolant system burp attempt. Let it cool overnight. Use one of the Haibeck methods. I use the one where you jack up the passenger side and fill. See if it burps any air that way.
Given the low miles, radiator fouling is less likely. But not impossible since you don’t know how it was used. More likely is that the thermostat is not fully opening. This is simply a function of age and well documented my Haibeck.
I had all the above on my last Z with only 48k miles on it. I ended up with a new thermostat and a new radiator. The radiator was clogged with sand in the fins.
H
