Which is the best Clutch fan, I have read about & seen all kinds used from T-Birds & curved blades, flex ...aluminum ...5 blades, 7 blades. I think I read aluminum tends to crack,
I bought a clutch but it will not fit my 4 blade non clutch fan. I found a 19-1/2" curved aluminum one but I wonder if straight blade steel fan is better... or what say you.........

 

Some of what you have in your post I think go for electric fan assy.?

I dont ever remember seeing a ALUM fan on anything, steel and stainless steel (after market) but not ALUM?
Note factory steel fan blades come it 2 flavors, direct drive that bolt to the water pump (may have a spacer between pump and blade) and clutch driven where the fan is bolted to the clutch and the clutch is bolted to the pump.

To get blades on & off a clutch you have to remove the clutch / fan from the pump and then unbolt the blade from the clutch assy.
I dont see the need to replace a direct drive fan blade with a clutch type if 1) it is keeping the motor cool 2) and if the motor came with a direct drive one.
BTW my motor, 300 six, should have a clutch driven fan because that is what the factory had when the truck has AC.
Well my motor had a direcet drive 4 fan blade with shroud and it keeps the motor cool other than if I sit for 10 to 20 mins, AC on and 95* out but as soon as I start driving the temp comes right down to normal.
Dave ----

 

There is no 'best'. I got one out of a '89 F250 for my 72. I bought a new Derale 18" for my 76.

Clutch is upgrade to a fixed fan. Less power loss, noise, cools just as good.

 

For Christmas, my Wife bought me a Derale 19" Clutch-Fan. It is the D17119. It gives about 3/4" clearance around the shroud opening.
Looks like a 1.5" spacer is required for fan 1/2-out, 1/2-in shroud spacing. You will need 5/16-24 bolts to go into the stock hub/pulley.
It is a very hefty 6-blade fan. Paint and quality looks as good as stock or better.
Spacer and bolt can be sourced from etrailer. They were the only source for 1.5" spacer. Fast, and good communications. I like these folks.

They have a different one with steel hub and aluminum blades. Lighter, likely a good choice also.

The original was 5-offset-position-blades. The space gives more room for bolting things up, and turning the engine manually.

If you are converting from the stock solid setup fan, you can't use the original 3" spacer. It is too long. As the assembly goes into the shroud, it hits the angle on the inside. Aim for a depth that puts the blades half-way into the plastic shroud.

That fan fits two different mounting sizes. Note that the Clutch fan bolts directly to the back of the clutch, in a larger circle. Then, the shaft bolts to the adapter and on to the pulley. That is why it takes a different fan, with the big precision hole in the middle to locate it exactly.

Fan-Clutch: Four Seasons 36954. A very generic and easy to find unit. Often mentioned for a Camaro. Fits: Buick Skyhawk, Buick Skylark, Buick Special, Cadillac Series 60 Fleetwood, Checker Deluxe, Checker Marathon, Chevrolet Bel Air, Chevrolet Biscayne, Chevrolet Camaro, Chevrolet Caprice

I can't see why anyone other than 4x4 crawlers and mudders would want a heavy-duty clutch. Those turn up to 70-90% when hot. Good for a dump-truck or summer in the desert, maybe.

Sizes are almost all the same on these parts - generic. Fan pitch, and the degree of clutch engagement varies from something like 60-90%, but is always slower than crank RPM. Additional harmonic dampening is a side benefit. Do get one with the thermostatic coil up in the front. Why use power pulling air at 20 degrees?

I am very happy with my old Flex-a-Lite 19" reinforced plastic fan. It worked great in Nevada in the summer, and is in near perfect shape (12 years?). It is a bit much for anything other than summer and towing, but if you have an old half-plugged radiator then you might go that way. I drive mine mostly on the highway, in the cooler months now (No A/C), and don't need the extra fan noise and drag.

Update: Summer use is going well. I haven't put the 1.5 inch spacer in yet, and the cooling is very adequate. No towing or very high heat yet.

Ideas to get you thinking. Your airflow may vary.

 

I made a custom spacer on my lathe

 

I wish I had a lathe.........Your truck looks Factory-

 

I found out I need an 18 inch fan, so the D17119 is too big, but it is on sale @ $57.**. My shroud is smaller than I remembered. I need an inch on each side plus 1/2 in & 1/2 out as 1972-3/4 ton stated.
I am not in a hurry, but I found a used one is why I ask now. I got a great looking new clutch from a well known company for only $19 or so. I probably don't need one but I plan to add twin turbos one day & will need it then but I have always liked the idea of fan no stress to engine when it is not needed

 

I don't see why a 1" space should be an absolute requirement. Wouldn't 1/2" around the ends work? Don't think the engine mounts flex that much when they're in good shape.
Assuming that the fan can be centered in the shroud, I would expect half an inch to be adequate. Close, but adequate?
Smoky_diesel, is that a factory shroud? Looks more custom, or scored from another donor?
Do you have a body lift, or is that just how the fan and shroud line up naturally?

Thanks

Paul

 

I read the 1 inch on each side in an article researching this topic.........It MAY have been 1/2" on each side but I get confused easy..............ha......
It did recommend 1/2 in & 1/2 out.........
Anyway back on the road...........what u think about my original post questions ?