Radiator fans DeVille 5 blade, Eldorado 7 blade - late '60s, early '70s

[chrisntam]

Which one moves more air?  I guess this thread is more of a comment on the engineering and thought process behind which of these two fan blades is correct for a particular application.  My '70 Deville had the 5 blade on it from the factory, Eldo gets a 7 blade.   Surprises me that 28 more cubic inches requires a fan that is that much bigger.  I did install the 7 blade on my car and hope to enjoy the benefits of more air movement come summer.

Comments?

[TJ Hopland]

How about a side shot showing the curve and depth of the blades?   I'm guessing the Eldo one would move more air but it may not be as much more as you would think at first glance.

[chrisntam]

The 7 blade is installed, when I put them together, the height was about the same, as I recall.

[cadillactim]

If memory serves me correct, thy quit using the 5 blade and went back to the 7 blade. I think 70 was the only year for the 5 blade (although I think the early 60s had a one year only 5 blade). The 7 blade will move more air.

Tim

[Scot Minesinger]

The 7 blade is also used on commercial chassis.  I installed one on my car as well.  It does move more air, car runs nice in summer.

[cadillacmike68]

Whether or not a car has Climate Control is a deciding factor on what fan was used the car was built.

Does anyone know where I can get a genuine Cadillac 1970 fan spacer so i can use a clutch-less fan on my 1968??

[Scot Minesinger]

Mike,

If you want to use a clutch-less fan, the fan blades have to be designed for that too (flatten at speed), so you need a 1970 fan to go with it.  Anyway, I might have a fan spacer and 5 blade fan if you are interested, let me know.  My e-mail is rscotm@cox.net.  There were several years Cadillac used fixed fan, 1970, 1972, and 1976 for sure, possibly other years too.  The 1970 Cadillac came with a 5 blade fan with or without climate control, and a 7 blade fan for commercial and I guess Eldorado.  For Eldorado it was likely due to shape of car and air flow into radiator-same as Toranado (they overheated some when they first came out).

[chrisntam]

IIRC, the spacer on the '70 is about 3 1/4" long.  How long of a spacer is required for a '68?  I was surprised the one for the '70 was that long until I searched for one.

["Cadillac Kid" Greg Surfas 15364]

Chris,
The 7 bladed fan was part of the HD cooling RPO.  It came with AC, Trailer towing package, and by itself in various years.  The exact chronology of the viscous drive/variable speed fan is a bit "hazy".  This was the case starting in the 60's. 
The Engineering of the fan is simple.  In very simplistic terms, each blade grabs a "bite" of air equal to the area of the blade and pushes it in the direction the fan is moving. As you can see there is a substantial amount of difference in blade area between the 5 and 7 bladed fans, and of course the result is a greater amount of air flowing.
The actual difference in cooling here in Southern Texas is quite noticeable.

Mike,
Summit has just about every kind of fan spacer you might think of.  The spacer should move the center line of the fan blade just about dead center of the shroud (front to back).
Greg Surfas

[cadillacmike68]

I think I have a 7 blade no clutch fan. I can get an aftermarket spacer (I might have one already) but would prefer the original ones used by Cadillac.

[Scot Minesinger]

Mike,

As Greg writes the spacer for the fan must line up appropriately with the fan shroud.  Simply using a 1970 spacer might be wrong because the front clip sheet metal/fan shroud in relation to position of engine between the 1968 and the 69/70 Cadillac is likely different.  The position of the fan within the shroud as governed by the spacer is important.  Also make sure the sides and bottom of your radiator are such that in relation to shroud all of the air drawn by the fan moves through the radiator, rather than around it (path of least resistance).  No one inch wide gaps between shroud and radiator for example.  Measure the fan spacer you need as per Greg's write up and buy one from Summit Racing, they have numerous different lengths.

[Jeff Rosansky CLC #28373]

I'm sure there is a solid reason for the Eldo needing the 7 blade but my guess is that with the transmission in the engine compartment, there would me more heat to dissipate and less room for the hot air to exhaust.  RWD has the transmission heat further back. 
One concern I have about switching fans is how the blades flex and flatten out at higher speeds.  The flex would be engineered to fit the specific car.  Just because you have more blades doesn't mean you will move more air if it is in the the wrong configuration.  I don't know if that is a real concern or not, just something I thought of.
Jeff

[Jason Edge]

I have very little experience with late 60's and early 70's Cadillac Fans, but know they were constantly tweaking fans.  For my years of expertise - 1963 & 1964: In 1964 alone they went back and forth switching between a 5 Bladed Clutch fan and 7 bladed fixed fan for AC equipped cars 4 times that year depending on your cars production number, not to mention the non-AC fixed 4 bladed fan went through at least 2 design changes between 1963 and 1964.

Here is the info I have collected over the years on the 5 bladed clutch fan and other fans used in 1963 and 1964.

Information about the 5 Bladed clutch fan found in a writeup about the new 1963 390 engine:
"Dampening the noise.  A more gimmicky innovation is the centrifugal viscous cllutch on the five-bladed radiator fan use to pull air through both radiator and condensor on Cadillacs fitted with air conditioning.

Using a thermostat-controlled valve to measure out a silicone fluid between two clutch faces, the fan will barely turn at low engine speed and low outside temperatures.  It will speed up to 3,200 rpm at high outside temperature and highway speeds.  The reason for keeping fan speed down: noise reduction. It also saves a bit of power."

In another review:
"Even the five-bladed fan is to allow on air-conditioned cars, and it has a sensing device to maintain maximum efficiency for both speed and temperature."

in another review:
"Uneven spacing of the fan blades cut high-speed noise."

My opinion is that if you are not too concerned about a bit of extra noise at higher speeds, and a potential small loss in power, a fan like the 7 bladed 75 series fan might be the best fan to fight temperature problems.  The 5 bladed fan is designed to conserve energy and reduce noise by maximizing how it turns in relation to rpm and temperature.

Info on the 5 bladed Clutch Fan vs 7 bladed non-clutch fan
Late in the 1964 production year the 5 bladed clutch fans found on 62 & 63 series AC equipped Cadillacs were replaced with the 7 bladed fan similar to the one already found on the 75 series and commercial chassis body styles.   Per Serviceman Bulletin (May 1964, pg 24), there was a trial run of the 7 bladed fan for Engine Unit Numbers 095092 thru 096419, and switched over for remainder of the production model year after Engine Unit Number 116,400.  Also in 1963 & 1964 non-AC cars use a 4 bladed non clutch fans that went through a couple of design changes  (need to research more).

Per 1965 shop manual, all 1965 body styles had the 7 bladed non-clutch fan.
I guess for 1965 and 1966 they decided to stick with the 7 bladed non-clutch fan until 1967 when they introduced the 6 bladed clutch fans on AC equipped cars.  I have the 62, 63 & 64 Serviceman Bulletins, but not the 65 and later and don't know if they did any production experimentation as they had in 1964.

[cadillacmike68]

Ok, revisiting this.

I'm pretty sure my existing fan either has bent blades or is otherwise not moving enough air. The clutch is pretty new, but I never trusted those things, especially here in Florida, where it's Still over 95F daily. So I go twe more fans. They both look like they have better blades. One takes a clutch, the other does not.

1968-1973 take the Same water pump. There are 4 different Hollander's numbers for fans for 68, 69, & 70.

1968 and 69 without AC take the same fan originally 5 blades on 1968 but changed to 7 - No clutch). There is a different Hollander # for 68 and 69 with AC (6 blade in 68 vs. 7 blade in 69, both with a clutch). The 70 has a different number but the book says that the 68 w/o AC ( 7 blade fan fits the 70 (7 blade) if a 1 & 15/16" spacer is used. So there is definitely some interchange with the fans.

Strangely enough Hollanders has the no AC fan for 68 as 7 blades with the AC fan as 6. I'm pretty sure that was an engineering change because the factory manuals have it as a 5 blade fan (with No clutch). The 69 manual specifically states that both AC and non-AC cars have a 7 blade fan, but the non AC cars have no clutch and use a hub spacer. Since they both take the same non-AC fan as per Hollander, the distances between the fan and radiator are identical in 1968-69.

The problem is that over 95% (maybe more) of the cars had Climate Control, so finding a factory spacer is difficult. However, All 1970 used a non-clutch fan and a hub spacer and there's that note in Hollanders stating that the 68-69 non-AC fan can be used on a 1970 with a 1&15/16 spacer. So, there might be a difference in the spacing between 1969 and 70. HOWEVER, both years have IDENTICAL wheelbase and overall length. Hollanders does have two different radiators, but no dimensions are given for the 1969 one, so who knows.

I have 3 fans, 2 that use a clutch 6 blades on the car and 7 blades on the floor, and a 7 blade no clutch fan. It had the flexible blade extensions s for high proper high RPM operation. I'll check their diameters and offsets, but would still like to get a factory fan spacer if it is of a compatible length. Otherwise I have two here and will have one milled to the correct size if needed. One of them will fit.

[cadillacmike68]

I'm going to check the distributor vacuum switch before I go off changing fans.

[35-709]

Cooling fan spacers are easy to come by on the aftermarket.  In the link below you will see that Speedway has spacers ranging from 1/2" to 2 1/2' in 1/4" increments.

http://www.speedwaymotors.com/Aluminum-Fan-Spacers-with-Bolts,1842.html?sku=91015720-125&utm_medium=CSEGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE&gclid=CN6EkMjUsM8CFQ5EfgodeHgFig

Summit Racing also has them in various thicknesses ---

https://www.summitracing.com/search/part-type/mechanical-fan-spacers?ibanner=SREPD4

Also Autozone, Jegs, & Amazon all list fan spacers.  Probably available at any good auto parts store.

Having said all that, I may have one in my stash but I would have to find it and measure the length.

[cadillacmike68]

Thanks G.

If the factory 1970 spacer fits, I prefer it, but if it's too long, then I'll get a new aftermarket one (and I'll paint it Cadillac Dark Blue!)

[35-709]

"and I'll paint it Cadillac Dark Blue!"

  Fine by me but I think Cadillac left them in their natural aluminum state, but I should leave that to the engine paint experts.

[Scot Minesinger]

My 1970 fan spacer is original and natural aluminum, not painted blue plus fan blades are painted black.  The spacers sold by Summit are not easily distinguishable from an original Cadillac 1970 fan spacer, just get the right length so fan blades are in correct position with respect to the shroud.  I powder clear coated my aluminum spacer after media blasting, still looks great.

[cadillacmike68]

Scot, Summitt sells some 134 different fan spacers. Some look sort of like a Cercelée cross viewed on end. I could perhaps mill off the ends to make look more like the factory original. I did find a 69 spacer on fleabay. If it is not too long I'll use it. I'm not sure I can shorten it very much, there is a nub at one end and a recess at the other end. That would take several extra steps with a sturdy drill press or similar to get those ends proper. Plus, there is only so much material on the ends to mill away. But, we'll see.