Temp effect on engine performance
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
My 78 400 has a fan clutch. I am not sure which years and what applications got them. Many other 73-9 users have OEM units. Fan clutches have been around a long time. Some PO may have removed the fan clutches on some vehicles.
Lead Driver
Joined: May 2004
Posts: 5,033
Likes: 137
From: Maryville
You can tell it's factory, not aftermarket, looks like the arrangement that was on my 75 F-100 360. This 351m is from another truck, the one in my 78 dropped a rod, he had the pan welded up and reused it, but you could tell by patch placement that it went out the side of the block. He rebuilt the block and had the heads from the origional rebuilt, maybe the fan setup is from where the replacement block origionated.
What is wrong with running an aftermarket flex fan, I've always had luck with them in the past?
What is wrong with running an aftermarket flex fan, I've always had luck with them in the past?
Laughing Gas
Joined: Feb 2003
Posts: 1,234
Likes: 3
From: In the woods of Oregon
I'm running a flex fan again. They have always worked for me, and my thermo clutch went out. Cheaper to go with the flex. My temps are staying more even also, but my thermo was bad. Never heard of a flex grenading, maybe at high rpms, but I don't rev her up past 5000 so I feel safe. Something to think about though.
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
I have run a flex fan and I have seen what they do when a blade fails. They flex and crack. When they do a piece can fly loose which unbalances the whole assy and it explodes. The clutch fans are much better. They move air better than the flex units. They also release when the air thru the radiator cools down and they are not needed. The flex fan only disengages at high RPMs which is not where your truck engine operates. They are fine for racing applications but not a daily driver. They are more reliable than electrics but not as efficient.
I would rank fans for efficiency this way, first being best: Thermostatic clutch, electric, flex, fixed.
As far as reliability they go this way, first being best: Fixed, thermostatic clutch, flex, electric.
As far as instantaneous HP available: Electric, flex, thermostatic clutch, fixed.
Now there are some new hydraulic powered fans that use waste power off the PS pump that may have possibilities...
I would rank fans for efficiency this way, first being best: Thermostatic clutch, electric, flex, fixed.
As far as reliability they go this way, first being best: Fixed, thermostatic clutch, flex, electric.
As far as instantaneous HP available: Electric, flex, thermostatic clutch, fixed.
Now there are some new hydraulic powered fans that use waste power off the PS pump that may have possibilities...
Hotshot
Joined: Dec 2003
Posts: 18,423
Likes: 9
From: iowa
Eric I like the way you rated fans that seems about right to me. But I have to add to this, I have also seen clutch fans come apart and go through the radiator this has happened to me twice, and had one lock up, and have the blades come apart so personally I don't think any of them are totally safe on that issue.
I will say I always used to put flex fans on everything, but they do not pull nearly as much air as a stock fan period they have one purpose only and that is to reduce the drag on the engine which means in order to do that they have to reduce the blades to pull air through, and have had problems with them cooling on my engines that I used for towing my stock trailers even with 4 core radiators.
I will say I always used to put flex fans on everything, but they do not pull nearly as much air as a stock fan period they have one purpose only and that is to reduce the drag on the engine which means in order to do that they have to reduce the blades to pull air through, and have had problems with them cooling on my engines that I used for towing my stock trailers even with 4 core radiators.
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
Originally Posted by monsterbaby
...I will say I always used to put flex fans on everything, but they do not pull nearly as much air as a stock fan period they have one purpose only and that is to reduce the drag on the engine which means in order to do that they have to reduce the blades to pull air through, and have had problems with them cooling on my engines that I used for towing my stock trailers even with 4 core radiators.
I have had clutch fans lock up but I noticed their howling and replaced them before any damage was done. I have also had them get loose on the shaft but it seems that if you check them when you change your oil you will catch that. Of course they don't check that or anything else worthwhile at the quick lube places.
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Posting Guru
Joined: Dec 2002
Posts: 2,003
Likes: 2
From: chicago burbs
has anyone ever watched a fixed type Ford fan? the ones i've had were flex fans! you'd have to go back pretty far to find one that is just a solid propeller blade that doesn't flex. my 68 montego had a stock Ford flex, that baby made a heck of a breeze too!
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
I have a couple of stock Ford flex fans hanging on the wall. They are built a lot better then the aftermarket units. They have been superseded by the thermostatic clutch fans tho. The clutches just work so much better. Besides, they are a replacement item, part of that built in obsolescence.
New User
Joined: Jul 2005
Posts: 12
Likes: 0
Sorry for the question - but what is a flex fan? My Gran Torino has a fan that changes its pitch as the RPM goes up. i.e. more pitch at idle. Since I had my 351M modified to a 400ci, (raised compression, mild cam etc.) I notice it runs a bit warm (gauge slightly over half) if I idle for more than a 5 minutes, once driving its fine
I was wondering if changing to a radiator with an electric fan(s) would have better cooling low speeds?.
I was wondering if changing to a radiator with an electric fan(s) would have better cooling low speeds?.
Hotshot
Joined: Dec 2003
Posts: 18,423
Likes: 9
From: iowa
read the entire thread closely but the answer is that normally a properly setup factory clutch fan with the proper shrouds will be you most efficient setup. electric fans do work well but just don't seem to pull as much air.
New User
Joined: Jul 2005
Posts: 12
Likes: 0
Thanks - I have read read more closely and see the opinions that the best cooling is Thermostatic clutch, electric, flex, then fixed.
I may be missing something else since I am still not sure what a flex fan is, or what type I currently have. - my Gran Torino's fan changes its pitch as the RPM goes up, more air at idle, less as the RPM increases. The shroud looks factory, but I kow the rad and fan are new.
Thanks!
I may be missing something else since I am still not sure what a flex fan is, or what type I currently have. - my Gran Torino's fan changes its pitch as the RPM goes up, more air at idle, less as the RPM increases. The shroud looks factory, but I kow the rad and fan are new.
Thanks!