For those of you still running a fixed fan on the front of your slant, watch this video.

https://www.youtube.com/watch?v=ZXdLgaFXZzs

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1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH

I saw that. Pretty impressive. I would never run a fixed fan. Clutch fans are fine, but electric fans are best for fast engine warmups and minimal load (either throug the belts or the alternator) while the engine is running. Yes, electric fans will have a draw on the engine output at idle due to the alternator having to create electricity to run the cooling fan, but if the vehicle is moving enough air across the radiator to cool the engine without a fan, electric fans are the way to go.

Engine masters has done a number of very informative videos. Their exhaust and header videos are good, too. Just remember they are working on wide open throttle and high RPM situations. Their dyno pulls usually don;t even start registering until 3000 or 3500 RPM, which is just about max RPM for a street driven motor.

That's why I use a clutch fan on the HPAK duster... although I wish they had run an electric fan/alternator for real world comparison on this set up, it's a bit odd that they just drop the comment that the fan will draw 30 hp/amp equivalent and that's OK because the alternator is running and drawing that much anyway driving the car...

I believe the fixed 4 blade fan/ no fan slant six numbers are seen in one of the slant sickness articles.

I was surprised at how bad the flex fans were. Some A-bodys don't have room for clutch fan. The first thing I did to my truck is install a clutch fan that I had lying on the shelf. Time to try a e fan.

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1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH

Not a Mopar clutch fan, but I know of a fan from another make that is a clutch fan with the correct rotation that will fit in a late A body with a slant six.

With my truck, the electric fan never runs unless you are sitting in traffic. It gets up to 185-190 and that is where it runs. Big cross flow aluminum radiator keeps things cool.

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Hold yer horses, folks, and before jumping up and down about how a solid fan takes up eleventy million horsepowers, see (especially starting at the third paragraph) this post.

"Electric fans are best"? Sometimes, not always, and with a bunch of terms and conditions. "Clutch fans don't fit"? That's not necessarily the case, as Reed has said.

See here.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

One of the first upgrades I am going to do to my truck is replace the stock seven blade fixed fan with an electric fan.

Is your truck a 70's D series? If so, consider rerouting the alternator wire directly to the starter relay with a larger gauge wire. I have read stories of fires started at the bulkhead connector and the ammeter gauge when more current draw is added. An alternator upgrade will obviously add to the risk.

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1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH

Very true and informative articles, however they do not point out the fact that an engine make significantly less hp at those lower rpms. Taking less from less is still a big loss.

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1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH

Not really; air resistance rises exponentially with speed and engine output does not. So a fan takes a much, much smaller bite out of power at lower speed than at higher speed.

Also, this cannot be harped on enough: electric fans do not run "for free". It takes a certain amount of work to move a certain amount of air across the radiator. Whether the energy to do that work is put into the fan directly by a pulley spun by a belt driven by the engine's crankshaft, or by a motor powered by electricity generated by the alternator spun by a belt driven by the engine's crankshaft, that work is going to come from the engine. The advantage of an electric fan is that it runs only when needed (as determined by coolant temperature), not that it somehow does its work without exerting a load on the engine.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I agree with you here but the electric fan will not be powered much at cruise speeds in most cases. Only on hot days with the A/C on.

Maybe the way to go would be to build an efan with a permanent magnet motor that would generate electricity when it is not powered but being turned by the incoming air. The generated electricity could negate some of the power it consumes.

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1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH

That's right, but it's exactly my point about fixed fans: at cruise speeds, they're not sapping much power from the engine because they're not facing much wind resistance. And a clutch fan reduces that "not much" to "almost none".
Sort of like regenerative braking on electric cars. Interesting idea!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Yes, my truck is a 76, but by then Mopar had switched to shunt ammeters in everything.

Dan brings up a point I hadn't thought about- unlike a fan on a dyno stand, a fan in a moving vehicle with the motor spinning at higher RPMs won't have to draw all the air across the radiator. The vehicle will be driving through the air and forcing the air across the fan blades reducing drag. Those dyno test are deceiving.

I am still going to go electric because I have all the parts and thise seven blade fans are loud.

Another big advantage of an electric fan is that if you have A/C, a properly-sized and -installed E-fan will pull a lot more air across the condenser at idle than an engine-driven fan will, improving A/C performance.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.