Most radials like P47s/F4Us have cowl flaps I believe.
The P51, YAks has the scoop too.
If you play IL2, it's what the "R" key stands for. On the 109 it's like if the flaps "split open", I'm sure someone can post a picture. In WB3, the cowl flaps are automatic, as soon as you are on the ground.
IRL I use the cowl flaps when on the ground or on the initial climb out. In flight I use my eng temperature and I regulate it with the cowl flaps, but usually in cruise I keep them close. They are not really needed for the engine temp and I gain 5-10 MPHs with them retracted.