How effective are the hood vents?

From Dave Marshall: FYI just for fun One of the guys asked me about how big a difference the hood sidevents made… So it was about 74° out and we were out for a drive so I checked the engine temperature with the vents opened and closed, about 20 miles each direction. We were cruising on pretty much level ground, no wind, at 45 to 50 mph. The engine ran 9° cooler with the hood side vents open… :)