Let's talk electric fan shrouds

Keith Tanner said:

Curtis73 (Forum Supporter) said:

Keith Tanner said:

Note that the amount of airflow on the highway is nowhere near as significant as you think it is, especially if you don't do anything to release underhood pressure. Point a strong fan at the nose of a car and try to get the radiator wet using a spray bottle. Most of the air is moving around the nose because going through the heat exchangers is difficult and air is lazy. I have seen too many highway cooling problems fixed with fan upgrades to believe that the fans are not contributing - and I've seen crap fans and shrouds (looking at you, Mishimoto) completely destroy the ability of a car to stay cool on track.

Totally agree when you're blowing a fan on a car.  On the road it's a whole different thing.  High pressure in front of the grille and cowl and low pressure from the air moving under the vehicle (and the boundary layer on the road) make for a LOT of airflow through the radiator.  In fact, it's why many OEMs now use weatherstripping under the hood.  It's not for noise, (although it might help) it's to take advantage of the low pressure under the car and make more air flow through the grille.

I knew that would get mentioned :)

There's a lot less pressure on the top side of the hood than in the engine bay at speed. You can still pull a lot of pressure out of the underhood area with louvers and this will improve airflow across the rad. Helps with downforce, too - you'd rather have that air replace the low pressure on top than underneath.

One of these days I need to tuft the backside of a rad and stick a GoPro under there.

Yes on the go pro.  Excellent idea.

So, what's the solution guys?  I absolutely hate the fan arrangement currently on the truck; it has caused the death of at least two radiators through contact and removing the clutch has killed my thumbnail twice, it is literally my least favorite thing about the truck and this is a Forever Vehicle for me.  

Looking at the pictures again, is it possible to maybe modify the mounts to move the radiator forward slightly?  That would give more space for fans and might make it easier to seal up the gap above the radiator and any around the sides. 

In reply to rslifkin :

In the interest of looking at all options, its possible to get maybe an inch of space but I don't really like the idea.  It would be fairly involved and I would have to modify the next one the next time some shiny happy person drives into me in this horrible town.

https://www.ebay.com/itm/Radiator-Support-For-92-97-Ford-F-150-F-250-F-350-Assembly-Gas-Engine-/232572152585

Just zip tie the fans to the rad with no shroud and see what happens. 

No use in overengineering something if you don't need it.

Have you tried mounting the fans directly to the radiator like you showed in the first post? That would be my first step, it may cool just fine.

Edit: Robbie beat me to it

Curtis73 (Forum Supporter) said:

My old Impala SS didn't have shrouds.  It had two that looked like this.  Same thing was on the 9C1 caprice which was designed to sit and idle for hours at a time with a big all-iron V8.

Weren't these engines noted to have cooling system problems that could be band-aided with a colder thermostat?

GM was really good at not good enough engineering in that timeframe, if it could save a buck.  Look at the LT1 F-body fans for a better solution with properly engineered shrouds and cowled fans.

Pete. (l33t FS) said:

Curtis73 (Forum Supporter) said:

My old Impala SS didn't have shrouds.  It had two that looked like this.  Same thing was on the 9C1 caprice which was designed to sit and idle for hours at a time with a big all-iron V8.

 

Weren't these engines noted to have cooling system problems that could be band-aided with a colder thermostat?

Not at all.  They were noted to have cooling issues because of Dexcool.  The lower thermostat temp was a performance choice because of the reverse-flow cooling.  All the cops I know were pretty ticked when GM stopped making the Caprice and they had to do Crown Vics, partly because the Caprices could be abused for 100k miles and still idle in a New Orleans summer for 6 hours and never get above 180 degrees.  They were actually a bit over-engineered.  Mine had a fan that died so I was only running on one fan.  I never would have noticed if it weren't for discovering the blown fuse.

What about mounting the fans in a 'pusher' layout? I know I know, it's not as good as a puller for cfm but hear me out.

I have a flex-lite single speed 16" fan set up as a pusher on my GMW because I was unable to get any clearance between the fan assembly and the engine and needed a fan of some kind. It's proven to be fine when it needs to kick in and bring the coolant temperature down in stop/go traffic and on the highway the temperature sits around 170*ish, and that's with an OE style full aluminum rad and a small block chevy.

Food for thought.

Mr_Asa said:

So, what's the solution guys?  I absolutely hate the fan arrangement currently on the truck; it has caused the death of at least two radiators through contact and removing the clutch has killed my thumbnail twice, it is literally my least favorite thing about the truck and this is a Forever Vehicle for me.  

You've got this.  You can do it.  But there really isn't an answer I can give you.  The real thing here would be if someone out in the wild has already tried brand X fans and had success.  Scour the Ford forums and see what others have done that worked or failed?  But in general, there are so many factors involved that its hard to predict.

If I were doing it, I would start with what you have, zip tie it on, and see how it goes.  If it works, find a permanent mounting solution and keep trucking.  My post wasn't intended to discourage you, I just offered a counterpoint because I knew you might be unhappy if you forged ahead with the fabrication only to discover it ended up being worse.

You may have already done this, but try googling for some web hits on what has worked and what hasn't.  Where I might start is with OEM ford stuff.  I don't think the 4.9L ever used an electric fan from the factory, but its possible some of the later 5.0L OBS trucks did.  Possible to find one that Ford already engineered?  I'm thinking about doing that with my Mazda B4000.  Later Explorers and Rangers had electric fans, so I might hit a junkyard and grab one.  A good (but tedious) way to do that is hitting up Rock Auto.  Find your radiator and click the part number to see what else it fits.  Then go to the newest application (with something like a 5.0L) and see if that vehicle had an electric fan. 

This is my fan and shroud. Unlike the OP I have about as much space as one could ever hope to build a shroud. I made it out of fiberglass to be as large as possible with smooth curves for airflow. The fan is a generic "3000 CFM" unit from Summit Racing that doesn't pull more than 30A. I removed every other row from the finger guard to improve airflow. I've been tempted to remove them all and just leave the radial struts but I'm concerned about the rigidity of the fan. My fan kicks on at 205F and off at 185F (thermostat starts to open at 180F and is fully opened around 203F). It usually doesn't take any more than a minute or two to drop water temperature by 20F on a hot day. Cruising around it'll never go above 182F. Flat out on track I see 200F water temperatures on 95F ambient days. I've contemplated adding flaps to the corners were the curves are the most severe.

Sometime in the near future I want to build a much smaller, flat shroud that's only ~1 in. from the radiator. I have a vented hood and want to fully duct the backside of the radiator. The current shroud puts the fan too far back to do this.

That is a really nice fan/shroud setup!