Yup, there is. As you tool along at 60 mph (88 ft./sec.), air does not flow at that speed through engine cooling fin spaces. It takes pressure to push air through such fairly rough, confined conduits. For one thing, the boundary layer of stagnant gas near a surface resists being accelerated and offers resistance to flow. So what happens is this: Air hitting the front of your air-cooled engine decelerates, its original kinetic energy now becoming pressure. That 88 ft./sec. air velocity, if fully converted into pressure (called "stagnation pressure" or just "Q"), becomes 9.6 pounds per square foot. Not very much, so fins have to be spaced far apart enough for that little pressure to push air through the spaces between them.