My dryer quit and I am getting a strange power reading at the outlet
The readings you are getting are entirely correct.  The problem is that you are misinterpreting the results.  When we speak of AC voltages there are several types of measurements that may be taken.  Specifically of interest here are:

1) Peak voltage
2) RMS voltage

If you want to dig into the theory of this please see:

RMS Calculations

But the bottom line is that the relationship for a SINE WAVE is:

Vrms = Vpeak * 0.707

In your case you measured a PEAK value of 320V/160V.  If we convert to RMS we get:

320 * 0.707 = 226V
160 * 0.707 = 113V


These values are slightly low but well within the "normal" range of AC mains voltages.  The specification at the point of usage is 105%-90% of the 240/120 nominal which means that the H-H line should be above 216V and the H-N lines should be above 108V.

More on that here:

Voltage Range