[Phil Waterman]

There was a hot rod solution to the noisy fan on flat heads, my 49 Lincoln is fitted with one. Really quite clever it is an electric clutch on the hub of the fan shaft. Which had a simple sensor in one of the radiator return hoses when the return water go to 180 the sensor sent voltage to the clutch as the temperature increased the clutch got more voltage until it locked up. They even change the size of the pulley so at idle if the engine needed more cooling it spun faster than the engine. But when the engine was 180 or below the fan didn't turn so there was no fan noise. At road speed the fan is normally just windmilling slowly in the air coming through the radiator, strange to see the engine just after you stop open the hood look in the fan is turning as it slows down but the engine has stopped.

Lot of guys who have done the 235 or 261 engine swap on Chevy's have gone to electric fans but this dosen't look stock which is why I mention the electric clutch set up unless you know it is there everything looks stock. Might be worth checking some of the Hod Rod Flathead sites to see if anybody is making them still.