I am glad to be in such a knowledgable spot. I (being the newbie learning on my own with any type of help from this and other types of sites) have found that there is a small amount of drag from the battery when it uses the electrical fan. (that was on another 88 I had) I did however attach a second battery just for the occassion and had also started running a second alternator.
AS for the fan (NON-CLUTCH) I still run the stock fan on my '69 DELTA 88, and myself---have never run into an issue of so called *power robbing* from the motor? I guess I should check a little further, but as my OLDS is my daily driver, she still gets up and moves W/O hesitation...
One more thing... the helicopter sound? Never heard that one before? I would love to hear a sound clip of this and if I am thinking about it... sounds like a water pump going bad (i.e. bearings), or even the lifters needing some pump up... time will tell I guess...?