Originally Posted by crabandy
Not sure what is meant by “pressure in this configuration is much lower on top than the bottom?” Can you please explain?
When you're climbing, you're at a fairly high angle of attack. The pressure gradient around the airplane in that attitude creates a high(er) pressure area on the bottom of the cowling than in a normal flight attitude. This reduces cooling flow.
In that climb attitude, the top of the cowling sees a lower than normal dynamic pressure, and the sides are largely unchanged, at least in theory.
So, you may see more cooling airflow from equivalent sized vents on the sides or top of the cowling in a climb attitude compared to the same vents on the bottom cowl.
You'd need to test on your particular aircraft to definitively prove this.