I'm running a flexalite electric fan with the adjustable thermostat on it. Engine is a 258 with a 195* tstat. When should the fan turn on? Should it be before the tstat opens, or only if needed say at 200* or above. I am running it right now at about 195*. I adjust it with a cooking thermometer in the radiator, so that I know when the thermostat is opening and closing. Thanks

IMHO, I wouldn't have the fan turn on right when the thermostat opens. other wise its going to be running alot. I have mine set to turn on just as the temp starts rising on the dash gauge. durning normal driving the temp stays low and the fan doesn't turn on. if I have to sit at a freeway offramp for a while it will kick on, bring the temp down and then kick back off.

I've got two fans on mine, one 10" and one 12" with two thermostats. I've got them set so the 10" comes on at about 205, and the 12" starts at about 215.
Seems to be working out good so far.

I used to have them both on one stat and they cycled a lot and caused huge voltage swings (they draw about 15-18amps each) With the dual stat set up, the small fan ends up running constantly when I'm not moving, and the big one rarely come on.