Don You stated that a puller fan is more eficient than a pusher and my thinking is it because your pulling the hot air from your engineinstead of pushing the hot air back over the hot engine? That makes alot of sense but when I instlled my dual electric fans in my 37 chevy truck I origionally had them set to pull but for some reason wwhen sitting in traffic and they came on they would run about 40 seconds to cool the engine down. When I reversed the fan direction and had them push the hot air over the engine, thay would only run 20 seconds before they cooled the engine down. Now the 37 chevy has side vents which I still have and was wondering if that made a difference.