Heat soak/ electric fan

[Grey owl]

Was using the stock 5 blade fan, for the most part it worked fine. My set up has aluminum heads, intake and long tube headers. The aluminum heads and headers disapate heat faster. That heat was trapped in the engine compartment at slow speeds causing fuel problems.

I installed a 3000 cfm 16" electric fan, it moves a lot more air at slow speeds while in traffic, where it used to run warm in slow traffic up to 210 it now never exceeds 185. You can actually feel a strong draft in the wheel wells when the fan is on. So its pushing that hot air out.

Be careful when ordering you don't have much room, my fan is the Evil brand bought off Amazon its advertised as 2.5" but its actually 3.25. I have 3/4" clearance from pulley.

 

[Puffins007]

Can you send a link of the one you ordered?

 

[Grey owl]

If you go on Amazon and type in Evil Energy 16 inch fan kit it will come up.

 

[EPB72]

So your thread title had me thinking a little different , I’ve thought about this before and may dig into it ,,, SO with an electric fan you could set it up to run after shut down either ambient temp switch and or some kind of timer,,, , within a minute or so the radiator core should pretty cool and then airflow through engine compartment ,, after 3 min my carburetor was cool to the touch ,, grant once the fan shuts down things will warm up again but still be cooler then if not having the fan run ,,,,,,, FWIW I run a 06 jeep liberty 2 speed fan off 2relays and a bmw switch , I’ve never had high speed come on , and low speed cycles with not a lot of on time,, mostly temp sits at about 195 -205’ with a 195 tstat..

 

[Grey owl]

Sounds like a nice set up, my goal was to address and mitigate the low speed temp increase I like to keep it under 200. Expelling the hot air from under the hood is helpful and important. Heat soak at slow speeds creates all sorts of issues but its effect on the fuel was the main concern.
I may consider some additional venting in the hood as well, the problem is finding vents that don't look completely out of place. The other option is a hood scoop, there are several that look right at home on a vintage Bronco.

 

[nvrstuk]

Grey owl... or vented inner fenders. I tubed my frt end and of course the inner fenders are gone and there is an amazing difference in heat under the hood

 

[Grey owl]

I thought about that as an option i ended up for going the hood scoop in favor of these vents. They are on either side of the carb they certainly vent a lot of that trapped heat

 

[Broncobowsher]

Hood vents are location matters more than most people think it does. I wish I could find the graph of positive/negative air pressure on a fairly boxy car shape.
The hood has 2 areas of positive pressure, the leading edge and maybe the first 6 inches. Then the back of the hood by the windshield. Why the cowl induction hoods work.
There is an area of low pressure, it is at the front of the hood. From about where the radiator sits that goes about a third of the length back. If you are trying to get heat out, that is the place for vents. Low pressure above the hood will help pull air out. If you look at an original GT40 it has the same concept for extracting air coming through the front mount radiator.
The further you place vents toward the windshield the airflow starts pushing air into the engine compartment instead of letting it out. A lot of people are confused because the can feel how air coming out while stopped, they are not considering the air pressure from actually driving.

 

[Grey owl]

The 17 inch electric fan is higher on the rad than the stock fan and moves more air across the top of the engine. Since heat soak is worst at slow speeds when pressure changes caused by air flowing over the hood don't really apply the air moved by the fan is important.

The best way to see the air flow over the hood at different speeds is by taping a 3" piece of wool on several places on the hood and driving it. I spaced these vents 8" apart in the center of the hood, that gets them over the valve cover.

I find the fan doesn't run at speeds over 30 mph at all but at slow speeds holds the temp to 175 degrees by providing a higher volume of air. With the stock fan the temp creeped up to 210 while sitting in traffic idleing the stock fan could not pull enough air at slow speed .

I should note i use an aluminum rad, they dissipate the heat differently than copper core rads. Right or wrong my observation is more aluminum engine components contributes to heat soak at low speeds. Long tube headers get very hot and dissipate heat much faster tha cast manifolds. Its the cumulative effect of these components that the vehicle was not designed for.

 

[DirtDonk]

All this airflow talk makes me think about a pair of winglets, or one long curved air foil, glued or screwed under the bottom of the hood near the rear edge, just in front of the cowl, to divert Hot under-hood air, more downward and out. Rather than up and onto the cowl area. Where it heats up the interior, and your feet and face.
No idea what it would do to engine tips, if anything, but I’d be curious to see if it helps cool down the interior.
After all, it’s not all coming from the forward facing firewall. Some of the heat probably comes from the top surface of the cowl, where it’s flat and captured under the hood.

 

[nvrstuk]

The 17 inch electric fan is higher on the rad than the stock fan and moves more air across the top of the engine. Since heat soak is worst at slow speeds when pressure changes caused by air flowing over the hood don't really apply the air moved by the fan is important.

The best way to see the air flow over the hood at different speeds is by taping a 3" piece of wool on several places on the hood and driving it. I spaced these vents 8" apart in the center of the hood, that gets them over the valve cover.

I find the fan doesn't run at speeds over 30 mph at all but at slow speeds holds the temp to 175 degrees by providing a higher volume of air. With the stock fan the temp creeped up to 210 while sitting in traffic idleing the stock fan could not pull enough air at slow speed .

I should note i use an aluminum rad, they dissipate the heat differently than copper core rads. Right or wrong my observation is more aluminum engine components contributes to heat soak at low speeds. Long tube headers get very hot and dissipate heat much faster tha cast manifolds. Its the cumulative effect of these components that the vehicle was not designed for.

All the 7 blade Bronco fans pull more air than any (99% of) 17" electric aftermarket fan.

 

[nvrstuk]

Eric and I did a trail mix test when driving back from the Rubicon about 20 yrs ago.

He didn't like raisins and I can't eat almonds so.... we got bored and of course I had my trail doors on giving us access to do this.... so we started tossing them onto the hood and they would end up at the base of the windshield. We solved the low pressure area debate... lol Almonds and raisins would sit on the hood for miles at 65 mph. Any other place on the hood and they were gone in an instant.
Edit/update: I need to add that it was 1100 miles home... so we had some free time

 

[ntsqd]

To hopefully better illustrate this idea of low pressure in the center of the hood look at this pic:

If the zone where those deep wells in the hood were at high pressure air wouldn't flow thru the radiator at all. Being at low pressure the air is fairly well sucked thru the radiator.
I don't know if the louvers above the front tires are merely venting high pressure air out of the wheel wells, or if they're able to create some down-force with them.


FWIW my '96 Bronco has a large rubber lip seal across the front edge of the cowl. As best as I can figure it's purpose is to keep engine bay hot air from entering the cowl vent to the interior. My old '88 4rnnr had a similar seal, for I'm guessing the same reason as commonly the interior fresh air is sourced from the cowl area at the base of the windshield. A whole page on the topic for the later trucks: https://www.garysgaragemahal.com/cowl-seal.html

 

[nvrstuk]

I'd drive that... except I'd want the rear wing to pop up like the Porsche ones do so I don't have to look at it all the time until it's needed at 160+mph.

 

[DirtDonk]

FWIW my '96 Bronco has a large rubber lip seal across the front edge of the cowl. As best as I can figure it's purpose is to keep engine bay hot air from entering the cowl vent to the interior

Not just the heat. But for safety, especially the potential fumes from fuel and exhaust.
Pretty much all road going vehicles had some form of seal ("cowl lacing") there because, especially back in the day of carbs and constant leaks, and even more so with road tubes and before EVAP systems, harmful vapors and even carbon monoxide getting into the passenger area was a real thing.
I'm guessing the old Jeeps and cars with "venting" through a fold-out windshield were excluded, but those with pop-up vents in the cowl area probably were where some of the early cowl lacing ideas and regulations(?) came from.

Paul

 

[ntsqd]

My uncompleted thought was that perhaps that p/n could be employed on an EB at the corner of the firewall-cowl junction to deny the engine bay hot air from getting into that small volume.

 

[Grey owl]

All the 7 blade Bronco fans pull more air than any (99% of) 17" electric aftermarket fan.

I have never seen a 7 blade early Bronco fan or even a 7 blade aftermarket fan, mine came with a 5 blade. So i am unable to comment on what a 7 blade fan does at idle compared to the electric. I do know the electric out performs the 5 blade at slow speeds

 

[nvrstuk]

... all I'm trying to mention is I see so many people go electric ( I work with a lot of hot rods rhat guys/shops have restored) & they all slap elect fans on & since they are relatively new tech - like TB fuel injection systems on sale everywhere, that they are the panacea to all issues. That's all- not talking down any- at all.

Here's Tom's Bronco parts listing as the 5 blade was a light duty/std & the 7 blade was the HD cooling option...and moves a ton of air.

 

[Slowleak]

I have never seen a 7 blade early Bronco fan or even a 7 blade aftermarket fan, mine came with a 5 blade. So i am unable to comment on what a 7 blade fan does at idle compared to the electric. I do know the electric out performs the 5 blade at slow speeds

A few years ago I tested about 5 different fans using an anemometer to measure airflow thru the grill. The 7 blade Ford flex fan had roughly 70% more airflow (cfm) at idle than all of the others. The one I have is part# CF-D4TA-8600-HA.
I will see if I can find the thread were I posted the results. Tom’s sells that identical fan.

7 Blade Radiator Fan, SBF V8, 1966-77 Ford Bronco

66-77 Ford Bronco components: Upgrade your 66-77 Ford Bronco with our 7-blade radiator fan. Perfect fit for V8 engines. See deals inside!

tomsoffroad.com

 

[nvrstuk]

I remember reading that article slowleak (don't know your name) and I had done a couple radiator torture tests a decade plus ago with different fan combinations and after reading your write up months ago I just got a handheld wind speed/cfm indicator... thanks for the time spent on that!