Never heard.............what pound of radiator cap are you using?    How old is the cap?
6s6

Nos681 wrote:

Are there any arrow marks on fan hub?
Might be on one side only.
The center appears to be leading edge and outside rim is trailing edge.

While fan is off car, operate fan in both directions…just by reversing positive and negative.
See which direction moves the most air.
Could tape it to cardboard box so air

has to flow through…even scrap pieces around perimeter.
Or just leave it on the shroud.

Sure wish these aftermarket electric fans were better marked.
Even my old Hayden 16” fan, had polarity backwards.
I had tested to verify before mounting it.

According to the pic, if the yellow arrow is rotation, then it appears it would be trying to blow air back into the radiator, assuming the fan bolts on the engine side of the radiator. That would definitely cause backwards and very ineffective airflow.

Nos681 wrote:

Fan guard is behind fan blade in the picture.

You are right, Dan. I was looking at it wrong.
Not sure it matters, but two 12” fans are pulling the same area in square inches area as a 17” fan.

Two 12” fans have 76” of circumference length while a 17” fan has 54”.  I wonder if there is more loss in efficiency due to the extra length around the perimeter. Probably not enough to induce the kind of problems experienced here.

Nothing wrong with a properly installed and engineered electric fan, but apparently something is amiss here that we are not seeing. My main opposition to electric fans is the typical lack of those two attributes in most installations. No idea if that is the case here or not.

I did the math before I posted

“Same” equals damn close

From the time I have had my car till the last changes it has had numerous configurations of electric fans, none of which was because of overheating.
The electric fan “folly’s” were more to do with ridding the engine of a belt driven fan. I have had pushers, pullers of various manufacture, none of which were all that great.
The only configuration that wasn’t tried was a o/e Contour two fan set up, which I found out later was the way to go.
The present set up is a mechanical 17 inch 5 blade Ford fan cut down to 15 inches with a custom made shroud on a 24 inch Champion rad, 180 “T” stat.
The Champ rad is not as pretty as some of the others but the price was right.
I had no room for a thermo fan so this one is direct drive.
My Autometer temp gauge very  rarely ever go over 180 indicated, an infra red point and shoot gun says 195 at hot side of the t stat housing.
I have no concerns about the small HP loss with the mechanical knowing that under sweltering heat with the air on in traffic the 331 is not going to go ballistic.
I am also quite sure that the removal of the o/e power steering system was a major contribution on lowering under hood temperatures.
I’m with Steve on “ I don’t need no stinkin electric fan”
YMMV

Toploader wrote:

A buddy of mine initially fitted an aluminum radiator and an electric fan set up. Last I heard he ditched both and went with a copper/brass radiator and a mechanical clutch fan.

Smart guy👍🏻