Hi Bolters,
I have a six blade, 18-inch fan on my 3800. Trust me, it's necessary. It keeps the engine cool but it's noisy, it uses extra fuel and takes significant power to run. I've tried electric fans but the 16-inch pushers don't move enough air. At one point I had two, a 16-inch pusher and a 10-inch puller and it still overheated on a long, hot pull and cooked the diodes in the alternator. Think 7-mile Cabbage Hill east of Pendelton OR on a hundred degree evening, foot to the floor, lights on, flashers going, 35MPH.
So for now I live with the downsides of a big fan but I would like to devise a fan clutch such as is used on big trucks so that the fan runs only when needed. I researched viscous-drive fans and the only one I could come up with that might have worked was listed for Jaguar sixes and didn't swing a big enough fan. I thought of adapting an A/C compressor clutch but the water pump still needs to turn all the time. On bigger Ford trucks of the era, like an F8 I once had, the fan is driven separately from the water pump. That would have made it easy but GM? No.
I'd love to hear any ideas you all might have.
