To some minimal gains are a big deal... Engine masters also did a comparison video showing loss from high amp load on an alternator (less than 2hp) and the difference between a mechanical water pump and an electric water pump which was a whopping 5hp.... The difference between an air gap intake and the stock aluminum piece is only about 8-10hp im told yet so many do it. I already had the higher output alternators which was a bolt in so I just spend the extra $200 or so on the fans, controller and wiring which honestly was easy to install and gives me piece of mind knowing I have redundancy from fan failure overheating issue with 2 separately wired fans. Is it something I would do to an otherwise period correct engine bay? No. but It was a very worthwhile improvement in my case and I have no regrets except not doing it 9 years ago when I originally was going to and instead wasting time and money messing around with the stock setup which worked but left temps creeping up while stuck in traffic and often sounded like a helicopter winding up to take off.

 

The free HP is nice. If you have 1240 RWHP, you might not notice the difference. But with only 240 HP (or less), every bit helps.

But I didn't go to electric fans for the free HP. Look at how much room there is without the stock fan shroud and (always spinning) clutch fan (post #3). That alone is worth it to me. Even if you count the alternator, the whole project cost less than $400-, and since I enjoy doing electrical stuff, it was money well spent. That alternator will cover future mods, so I don't mind.

To answer @CorvettePassion's question:

Selectable cooling: Depending on your fan controller (or your ability to program an Arduino, or however you want to solve the problem), you can have the fans come on as needed, or with the AC, or on demand manually, or stay on for a period of time after you shut down the car.

The tremendous space savings (as mentioned).

Due to the orientation of the C3 radiator, there is likely less airflow under the hood. I have a dual-snorkel CAI in both cars, so I don't care. My 80 (with electric fans, side pipes, and not much insulation) is cooler inside than my 79 (with the stock clutch fan, under the car exhaust, and lots of insulation). Both have the heater circuit bypassed/plugged, no A/C, and the same Lars-style tune.

 

Thanks for the input. But, the boldface comment above concerns me. I honestly believe one reason my 77 has no heat issues inside the car is because my engine compartment is very open, i.e. no AC, no emissions, i.e. lots of room for air to come into the compartment, and vent out the side vents. So....as you suggested, and others have said, electric fans are pointing down because they are mounted on the radiator VERSUS the airflow coming from the clutch fan / shroud, blowing directly back across the top of the engine.....and then flowing out the side vents.

However, you are stating you have LESS heat inside the car with the electric fan setup.......Problem is, it could be other things in play.

So still not sure which type of fans ventilates the engine compartment better. I wonder about that big open space provided by the missing fan shroud....what are the aerodynamics there....does that provide airflow from under the car....that is typically blocked by the fan shroud. Hard to know.?????

 

I took the time to carefully write what I wrote, and I tried to declare all of the relevant variables. Each car is different, and the location of the exhaust seems to matter a lot more, at least between my two cars.

Your engine is not cooled by air flowing over it. It is cooled by water flowing through it.

I do have this data. During this particular run, the fans never came on. Ambient air was measured under the front bumper, compartment air was behind the air cleaner assembly, intake air inside the air cleaner above the carb. Again YMMV, but it seems that if you spend a lot of time in traffic, you'll need AC and an on-demand electric fans.

 

Yes,.....I know it is not an air cooled engine. And this is often confusing when people talk about electric fans versus clutch fans. You have TWO things.....one is engine temperature, which is dictated by many things, but radiator effectiveness being very important. Clearly....electric fans are better for engine cooling, but I also know that electric fans are often added when a new ALUMINUM radiator is installed. Two changes at the same time....with the fans being given the credit for the improvement, when in reality the new and better aluminum radiator could be a big part of the improvement over an old radiator.

But,...my question is more about engine compartment heat....NOT engine cooling. Engine compartment heat becomes heat back into the car and on us passengers. Much of that is mitigated by proper rear hood seal, foam horseshoe collar over the bell housing, good seals on all the heat box doors, etc. And then, the firewall needs to have no holes, and the insulation in good condition. All of those things that Chevy put in place when new need to be still functioning properly. In my 77, I used Lizardskin ceramic spray over the entire inside of the car, as well as Lowes Reflectix under the proper jute backed carpet. In my 77 there is ZERO,....and I mean ZERO heat from the engine compartment into the car. I can drive on 90 degree day in summer comfortably....and in reality my right foot is only inches away from the headers...NO HEAT ISSUES. And I do not have AC.....don't need it, don't want it.

I believe one reason for this is that I have airflow into and out of the engine compartment, out through the factory 77 side vents. So, again.......do electric fans, mounted at a down angle, that only run when engine is hot enough, going to ventilate the engine compartment like the factory fan shroud / mechanical fan......that is blowing air through the compartment, top down, all the time...even if it is hot air,.....its moving air.

I have read multiple posts on this, with lots of theories about what the airflow is actually doing....but every car setup makes it a different scenario. Modern cars are packed to the gills wth stuff.......ZERO airflow. You open the hood....its solid. My engine compartment is uncluttered, and open because I toss most of that stuff in the garbage.

Its just a question, and maybe my theory is wrong. My main reasons for NOT wanting electric fans has to do with my basic premise to stick with original on this car, plus modifying stuff is a rabbit hole....one thing leads to another. I am not really interested in electrical mods. Lastly....I hate the look. I WOULD like the open space around the front of the engine, especially when I have to work down there.....big block will only make it worse. But that is not enough of a reason. The BIGGEST reason I would go elecric fans is if I cannot figure out how to get a spreader bar installed......THAT is a mod worth doing.

By the way....my 406 SBC powered 77 Corvette has Dewitts aluminum radiator with factory shroud and clutch fan........runs 180 degrees ALL THE TIME, stopped in traffic, whenever. Never had a problem with it regarding engine temperature.

 

I have a dual digital air temp gauge with a temp sensor mounted near my passenger head and another temp sensor mounted in my cowl induction air filter... The air filter is typically at air temp or sometimes a couple degrees less while moving. The other sensor mounted by the head is typically 10 degrees hotter unless the car is sitting at a stop running for a while, Then the temps do creep a bit but honestly they are still lower than I would imagine they would have been. My theory, The hot air being pulled from the rad is blown down under the engine and not across the engine but the airflow pattern ends up pulling cooler air into the engine compartment in the form of negative pressure it creates kind of like a venturi effect.

if your 406 is always at 180 you are lucky. your clutch may be locked up though and always spinning the fan robbing power also as many old original clutches are at this point. id check this and think about at least replacing the clutch. If you dont want electric fans that totally your choice. You have your reasons thats all that matters as far as im concerned. I'm just trying to point out they do in fact generally perform better than other setups and use less hp if any only when turned on when thats a priority but everyones wants and priorities vary. Is it needed? No, neither are any performance upgrades.

I have two engine temp sensors and found I had to increase the temp for when my fans come on with the 180 degree stat because even after installing a second high flow 180 degree stat last week I got the same results because my engine still hung around 165 and never wen over 174 I attribute this to the stat being partially open before the 180 degrees and the fan controller I have I bought used was set for the fan to kick on around 160.. The last guy must have had a 160 degree stat. Now with the adjustment the car is typically in the high 170 to low 180s. The same rad and stat with the stock clutch fan and my engine hung around 200 degrees.

 

My mechanical fan clutch is was bought new when I restored the car, and 18,000 miles later it still works. I really don't believe it is "lucky" that the stock mechanical fan / clutch maintains temperature at 180. The entire C3 generation used clutch fans, and if car is equipped as manufactured with parts that work, seals that are intact, and radiator that is functioning properly, then the system works. Electric fans were introduced to cars near the end of the C3 generation, and are the standard today. I am not speculating as to why or what is best.

I can tell you that as soon as I read about "fan controllers" and "sensors", ......I run away. Probably fear of the unknown,....but it also just starts to take the car away from what I love about it. If I do an electric fan conversion, it will probably be Dewitts, with the in-radiator sensor, and whatever wiring they recommend. I won't be adding "controllers". With that installed, it suddenly becomes something I don't want.

As I have said before,....if I want modern stuff, I would just buy a C5, C6 or maybe a C7......but I am quite sure I would not find those cars to be as satisfying and fun as mine.

 

I understand your point of view.
Theres no speculation involved though if we are talking technology alone with no sentiment or otherwise. The electric fans are a superior system for most applications, just as the LS1 is superior to the older gen small block for performance capability. But I think we all agree that doesnt necessarily make the LS1 the best replacement for all the sbc applications out there either.. Like I said earlier if I had a "restored" or original car I wouldnt change the clutch fan system.. If my car was modified for performance I likely would. The OP here bought a modified car with a non original crate engine and improperly functioning electric fans. Theres a lot of c3 owners here in the performance section that have modified thier cars for performance. Thankfully its up to the owner to draw the line where I respect thier choices but will comment when they make unsupported claims about thier decision while more of less criticizing others to support thier own choice.. There are lots of cars purchased or inherited with improperly setup or garbage quality fans and those tend to be used to justify a mindset that they are all this unreliable over-complicated completely unbenificial thing. I commented to support that they are not.
Its really a lot like digitally stored music offers superior sound reproduction to vinyl regardless of enthusiasts who prefer vinyl. They have their reasons, whether nostalgia or otherwise.


As far as that "luck" It was my understanding the "stock" system is supposed to keep the engine between 200 and 220. I didnt think the clutch was supposed to lock up enough at such lower temps to maintain them is what I meant. I guess in your particular case the wide range the fan is always locked up is a good thing. mine ran at 200 even with the 180 stat, 3 row aluminum rad and all

The later year c3s were equip with an electric auxiliary fan to help the improve the dismal cooling of the c3 cooling system as well as help with engine cooling while the ac is running Ive read. and your right it wasnt until 82 that they switched to fully electric dual fans with the 84 model year car, I had one of those, And I would be lying if I said I never had an issue with the engine overheating as I did once in the 13 years I had the car when the fan temp switch failed so that would be one plus for mechanical systems... That is a possible failure I addressed with my current car as it has a manual override switch to turn the fans on if that ever ocured

 

@Tony53 hoping to get you fixed up! post as many pics as you can...there is a wealth of knowledge here who has helped me a lot..and pics are VERY helpful.
on a side note of this thread..
I think the bottom line is everyone has a reason or intended purpose of fans all justified uniquely .
My purpose is spirited street and to return to 1979 with ac when wanted and to try and get as close to driving a new car off the lot reliability and perform like one.
I had the rare opportunity last couple days to have record heat and dew points in the last decade..96f with sun glass t tops, and dew points very high..
My 79 is an L82 manual , no cat duals, factory manifolds ( no headers until i am confident of heat fitment issues someday) with dewitts universal fit aluminum radiator AND my auxiliary factory electric fan which come on now modified with AC along with factory original 5 blade clutch fan with all seals in place. so i have both (when AC on)..
i also have as much heat mitigation as i can under hood, factory heat shield etc..switch to 180f thermostat from factory 195f.
Sitting in traffic, ac going from 43f to 52F inside vent.. and finally the temperature needle moved about 2 needle widths.. i can only imagine the factory set up was worse in 1979 (thus the additional electric fan from factory to come on over 230f).
In additions to what what was already mentioned..and some great data shared from many.. my application intended purpose requires...
- a thorough inspection of existing radiator. Without a doubt this needs to be efficient and aluminum is an obvious upgrade and should be considered. As mentioned often both fans and radiator are replaced.
- a good working fan clutch seems to be the optimal set up if mechanical to bring the airflow when needed. It only reasons that a fixed fan will outflow a clutch fan IF THEY ARE THE SAME BLADES, but i have no clue about airflow of a flex fan compared. I wish they would have measured that as well in the dyno tests.
- i wonder how many heads cracked stories on later c3's due to very high water temperatures? many of us have 195f thermostats...makes no sense to run that hot if heat is an issue, 180f should be fine.. i get that it is a thermostat but at least you start form a lower set point when temperature increases.. and it will.. the aux fan is set for over 230f! in 79.
- a good tune on timing and fuel... cannot say how much the performance timing set up and advance helped my car.. and then carb tuned (Lars rebuild).
- seals, shrouding, fan placement, and common sense airflow blockage inspections

 

I don't believe my new fan clutch is "always locked up".......but honestly, I have not looked at it. I start the engine, and drive the car. I don't hear this "loud fan noise" that so many people talk about. My engine sounds like a car engine.. Car has great sounding exhaust....I drive with the T-tops and windows down ALL the time. So, there is lots of noise. No one sound is more or less annoying than any other. Car sounds like a car. So for me.....whatever this "fan" noise is,.....its irrelevant to me, and I doubt I would be one ounce more satisfied or pleased without this apparent noise.

If there is a way to check to see if the clutch fan is "always locked up"....let me know, but frankly, I am not doing anything about it if it is.

 

Basic Clutch Fan Check:
start your cold engine and turn it off after 1 minute.
Check the resistance to turn the fan blade.

Restart your car and let it get to the operating temperature.
Turn the engine off, the fan should have more resistance when hot.

 

I have a real world anecdote that has pushed my opinion hard in the direction of electric fans.

I got caught in I-95 traffic for an hour. Stop and go, 0-20. No AC, windows down, and as good of a tune as you can get from a 79 L48 with stock exhaust logs. Stock radiator and clutch fan. This was a hot day, temps approaching 90, partial sun, black car.

Anyway, the engine did not overheat. I was watching the gauge. It stayed at 180 degrees the entire time (180 degree high-flow thermostat). It's been calibrated with an IR thermometer, engine temp was not a problem for the stock clutch fan.

However, the brakes overheated (!). My brake pedal went soft, and by the time I was able to work my way to an exit, the "Brake" light on the dash came on, indicating that the combination proportioning valve had done its thing and blocked one of the brake circuits.

I parked, popped the hood, and let the heat out. Nothing under the hood was cool enough to touch without burning myself. The upper radiator hose was the coolest thing there, since it was fixed at 180ish degrees. After 30 minutes, with the engine cooled, and my brakes functioning, I was able to find an alternate route with a higher average speed.

If I had encountered this situation in my 80, I am confident that I could have run the fans at full blast, full time, and only be limited by my idle charge current. Certainly, even aimed at the ground, the extra airflow would have been better than the stock clutch fan turning slowly. It's hard to repeat the experiment with the 79, but I have a set of dual fans on the way that I hope will solve the problem.