Two Cents on Electric Fans

[John Palmer]

Have you driven the car at highway speeds "without the shroud installed"? 

Did it still overheat?

[lalessi1]

My thoughts are the fan shroud is the problem. (4) 3" holes will increase the fan shroud open area by 15%. The calculations are based on simple area but aerodynamics calcs are  not that simple. The shape of the shroud is really not an issue at low speeds. I was waiting for the thermostat conversation, that is not that simple either IMO. Heat transfer flow rates for flowing liquids is not a straight forward thing. I am not convinced that slower flow rates on either side of a liquid to air heat exchanger improve heat transfer. If I was racing I would run a restrictor plate because it would reduce the HP draw of the water pump.

The engine did not over heat on the highway without the shroud but that was with the mechanical fan.

The thermostat thing is an easy test, I was going to do that anyway. I love the idea of "popping" the hood, thanks John.

BTW I really enjoy the conversation!

[Ford Blue blood]

I agree, the fan shroud is the most likely cause.  Late model cars do a lot of engineering to control air.  That includes not only air flow but computer control as well.  We have one thing we can control, or at least moderate.  Getting air out is as important as getting air in.

Short story, I repainted the fenders on my 36.  When I put them back on I left the inner panels off.  When running down the road the car would run hot (220 - 240) and cool off in town.  This situation crept up on me as I did the paint work in the fall.  It showed it's ugly head when summer got here.  Ran that way for two years.  Decided to install the inner fender panels and the heat problem went away.  Only conclusion I could come up with was air staying in the engine bay (very small on hot rods) and restricting air flow.  Car now runs temps that are normal.

[John Palmer]

Bill, great point.

It reminds me of the Myth Busters episode. They were asking the question about the pick up tail gate "up, or down" to increase fuel mileage.  The conclusion was, when the gate was up, at highway speeds, the bed filled up with "air pressure", it improved the vehicle aerodynamics and it improved the fuel mileage.

Air flow cannot get in, if it cannot get out.