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Mechanical fans push more air at higher RPM, but they reach a point of capacity where they overrun themselves and overtax the engine
YES! You did read something I wrote! Of course they do, never claimed otherwise. The dyno test is pushing them way outside of their efficiency curve and using gobs of hp unneccessarily.

Electric fans may not push as much at the higher RPMs and they to reach a point of limitation
Again, this is what I wrote above, no argument.

but they do not creat drag on the power plant or generate the resistance on the engine, or heat from drag.
No, 60a worth of fans costs ~2.5 hp. There's no free lunch. Sure, 2.5 is better than the 20+ by pushing a mechanical way outside of its efficiency curve but that's not what the argument should be here.

Maybe this is our disconnect, we're not even agreeing on the point being argued.

Did @sikryd want the absolute most electrically/mechanically efficient way to move cfm through the rad? No! He's got an overheating car because the 2730cfm of his dual Spal setup can't keep up.

The question is on cooling the car, moving the most cfms through the rad and therefore shedding the most BTUs to the air.
The question is not 'how can I get 20 more hp at high rpm".

I fully acknowledge that switching to mechanical fans will cost some power, especially up top where the mechanical fan of fixed pitch is being pushed outside of the rpm range it runs most efficiently at. That's not up for debate.

@sikryd is trying to solve a heating issue. I'm suggesting moving a lot more cfm through the small tri-five rad. I'm not saying those cfm will not cost power.
You're not totally incorrect, but you have flaws in the end result of your conclusions.
You're just misunderstanding my conclusion. I never claimed you couldn't save fuel/power with electrics. I love electric fans! If you're trying to move air though, crappy old mechanical fans move more air, at a cost.
 

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What I'm wondering about now, is how hot is too hot under the hood? With cooler weather coming and no heater, or side windows, I could use a little more.
 

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All this discussion about the conductivity of aluminum, steel, dry air, humid air, etc. is not all that meaningful.
It is a meaningful point when @sikryd started having heating problems when switching to a 3.5x more thermally conductive aluminum head.

Convective heat transfer is more dependent on surface finish and surface area. The main place where conductive properties affect conductive heat transfer are cylinder walls to coolant, as well as combustion chambers to coolant. Those are very efficient no matter what the materials are so while they matter, it's not what matters most.
While surface area and finish matter, 3.5x the conductivity is absolutely where the main difference is. Our surface area will be reasonably close between the two heads. Plug some numbers in to Fouriers law and see just how much difference in SA/finish you'd need to make up for 3.5x difference in k.
 
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While surface area and finish matter, 3.5x the conductivity is absolutely where the main difference is.
I have to disagree with that statement. While it's a reported difference, I think the real reason for the OP's problem is something that's not known to this discussion, at least yet.

Shifting gears a bit, there's been discussion of the giant potential for airflow of a mechanical fan spinning at high rpm, as well as the fact that it takes a lot of power to do that. But no one has mentioned the existence of fan clutches that eliminate much of the huge power draw. Bottom line is that fans are mostly needed at low road speeds. Unless you're towing heavy loads, going up steep grades, or racing, you generally don't need a fan at road speed. Mechanical fans get clutches, electric fans get turned off at road speed.
 

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I have to disagree with that statement. While it's a reported difference, I think the real reason for the OP's problem is something that's not known to this discussion, at least yet.

Shifting gears a bit, there's been discussion of the giant potential for airflow of a mechanical fan spinning at high rpm, as well as the fact that it takes a lot of power to do that. But no one has mentioned the existence of fan clutches that eliminate much of the huge power draw. Bottom line is that fans are mostly needed at low road speeds. Unless you're towing heavy loads, going up steep grades, or racing, you generally don't need a fan at road speed. Mechanical fans get clutches, electric fans get turned off at road speed.
Even clutch fans are a suck...watch that video above, it's not impressive
 

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I have to disagree with that statement. While it's a reported difference, I think the real reason for the OP's problem is something that's not known to this discussion, at least yet.
According to @sikryd (not the OP), the problem started when he switched to a head of 3.5x the thermal conductivity (and moved to Vegas, to be fair). I'm not calling this a firm diagnosis by any means, I'm just saying that we know a significant variable changed at the same time the problem occurred. It's not a stretch to think they could be related. Could it be another problem, got the timing / fueling wrong, or something else entirely? Sure. Absolutely.

Since apparently they've double checked the fuel, timing, all the basics and seem to be frustrated troubleshooting wise, a couple three hundred to get a cheap plastic shroud, plastic fan, and a fan clutch seems a pretty good next step. Doubling/tripling the cfm of air going through the rad has a pretty fair shot at solving the cooling problem as described if the basics check out as stated.

But no one has mentioned the existence of fan clutches that eliminate much of the huge power draw.
Agreed, a fan clutch is the way to go. I was trying to keep it simple as many hot rodders seem to believe that electric fans can somehow magically turn the same speed and push the same cfm for less power used and that's the fundamental physics misunderstanding I was trying to clear up. I'm still not sure I explained it clear enough, but gave it my best shot.
 
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I'm not calling this a firm diagnosis by any means, I'm just saying that we know a significant variable changed at the same time the problem occurred. It's not a stretch to think they could be related.
If you accept this logic, it would mean that aluminum heads are not a viable choice for a performance engine without serious mods to the cooling system - and that simply isn't true. It would also mean that performance relative to an iron head would be significantly lower because so much more energy goes in the cooling system, and that isn't true either.
 

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If you accept this logic, it would mean that aluminum heads are not a viable choice for a performance engine without serious mods to the cooling system - and that simply isn't true.
Any performance engine should prompt some cooling mods, especially in an application like ours with a smallish rad area. I think sikryd was probably borderline with cooling earlier, with only 2730cfm over a fairly small rad cooling a healthy big block. I think it's a fair possibility (not a certainty) that between the aluminum head swap, and as Robert pointed out, drier (and probably hotter) air, he went from borderline to right over the edge.

Like you said, there very well could be something wrong as well. Random thought, I don't recall hearing if he checked for gasket sealing issues as part of the basics. I've had a couple engines push combustion gases in to the water jacket, and if you want to see something add heat to coolant, oh boy does that do a fine job. There were lots of other obvious symptoms though, miss, smoke, milkshake, gas bubbles through rad, you know the usual stuff that I'm hoping he would have caught in the diagnosis.

It would also mean that performance relative to an iron head would be significantly lower because so much more energy goes in the cooling system, and that isn't true either.
Lower, but not significantly. I think you'd need a perfect lab experiment to prove it out, and we can't even get in that range of repeatability with back-to-back dyno sessions. Keep in mind as discussed earlier, 1 HP of energy turned entirely to heat is 2544BTU/hr. That's a lot of heat for each hp lost. You'd need to design a very repeatable test, laboratory conditions type of repeatable.
 

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You could get a mist sprayer to mist the radiator. Less and less efficient as the humidity rises. I imagine it would make the engine bay a mess, and really a mess unless using distilled water. Just pretend I didn't even mention it. ;)
I did this on my 1988 Mustang that I put a 460 in, I redirected my windshield wiper sprayers to my radiator. lol... Stupid kid I was
 

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Like you said, there very well could be something wrong as well. Random thought, I don't recall hearing if he checked for gasket sealing issues as part of the basics. I've had a couple engines push combustion gases in to the water jacket, and if you want to see something add heat to coolant, oh boy does that do a fine job. There were lots of other obvious symptoms though, miss, smoke, milkshake, gas bubbles through rad, you know the usual stuff that I'm hoping he would have caught in the diagnosis.
No head gasket issues at all.
 

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Let me add this, I rarely go on the freeway because of the 5:1 gearing in my 9" Ford rear end. I have 31x18 MT tires and an M21 transmission, it screams on the freeway, 60 mph is 3500 RPM. Most of my driving is around town, 45 mph or less. Yes, I moved to Las Vegas and only drove for a short time before changing the heads, so I am not sure if I would have had the same issue had I kept the cast iron heads. I replaced the heads, added the aluminum Dewitts radiator, the FlowKooler water pump, and still have issues. I don't have head gasket issues, my timing is set at 14 degrees initial, 36 total. My air/fuel is not lean or overly rich. I suppose I can test out the mechanical fan, but due to the fact that most of my driving is under 2500 RPM, will a mechanical fan help me there? The SPAL fans have 12 rubber flaps that open up at higher speeds, so I would think this aids in cooling when the electric fans reach their limit due to higher road speeds. I may end up looking at the shroud and mechanical fan, I certainly don't have the money for a Cold-Case or Be Cool system that thousands upon thousands of dollars.
 

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If you have a clutch fan, check the clutch...they wear.

If you have a mechanical and want to keep it, check your shroud engagement...most people get it wrong

If you want to get out of the stone age and have the $ means, run shrouded electric fan (or fans). They don't suck hp or make the engine work harder at high RPMs.

You may have other factors generating heat (headers). You have to address that..louvers work, second gen trans ams had functional louvers as air extractors and they worked well.

Your heads are not going to likely cause these issues and if you are running aluminum heads....still won't.

It's not a hard problem, but watching people defend antiquated things is no longer entertaining...lol...

If you really want good gouge on heat management, go to a SYTY forum...(Syclone Typhoon) they run high heat turbos, are GM....and high HP guys use extractors and electric fans....and all the aluminum parts you can shake a stick at.
 

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If you have a clutch fan, check the clutch...they wear.

If you have a mechanical and want to keep it, check your shroud engagement...most people get it wrong

If you want to get out of the stone age and have the $ means, run shrouded electric fan (or fans). They don't suck hp or make the engine work harder at high RPMs.

You may have other factors generating heat (headers). You have to address that..louvers work, second gen trans ams had functional louvers as air extractors and they worked well.

Your heads are not going to likely cause these issues and if you are running aluminum heads....still won't.

It's not a hard problem, but watching people defend antiquated things is no longer entertaining...lol...

If you really want good gouge on heat management, go to a SYTY forum...(Syclone Typhoon) they run high heat turbos, are GM....and high HP guys use extractors and electric fans....and all the aluminum parts you can shake a stick at.
I have aluminum heads and I have electric fans. I don't have the money for a cross-flow radiator. I have headers, they are not ceramic coated but are coated with that Eastwood header paint. I'm going to hang a thermometer in my engine bay to see what the ambient temps get to while driving around just so I can know. I don't think louvers will match on my 56, I don't think any scoops look good on a 56, I don't think running around without a hood looks good on a 56. Really the only thing that does is a tunnel ram or a blower through the hood, both of those I don't have the money for until my extortion payments stop to the ex-wife. Maybe it's time to sell my KTM dirt bike for upgrades on the Bel Air.
 

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Your recommendations don't appear to be based on reading @sikryd's actual problem.

If you have a clutch fan, check the clutch...they wear.
If you have a mechanical and want to keep it, check your shroud engagement...most people get it wrong
@sikryd already has electric fans.. 2730cfm if I'm looking at the right model.

If you want to get out of the stone age and have the $ means, run shrouded electric fan (or fans).
He indicated lack of funds was a major problem and that he did not want to upgrade his current fans to the latest greatest electrics. That's one of the reasons I made the recommendation to take what seems like a step backwards and go old school, just for cheap cfm. I'm not recommending old tech just to be a contrarian. I might not be a complete idiot.

They don't suck hp or make the engine work harder at high RPMs.
To repeat myself ad nauseum, yes mechanical fans use more power at high rpms when pushed out of their efficiency curve. Absolutely nobody is trying to say any different. The actual problem however is "how do I cool my car?", not "how do I save 20hp at 7000rpm?". He's not drag racing the thing, but apparently wouldn't mind being able to drive it without it overheating.

You may have other factors generating heat (headers).
I already recommended changing that out, it wasn't an option he wanted to go with.

It's not a hard problem, but watching people defend antiquated things is no longer entertaining...lol...
Glad you found it entertaining. I'm not defending antiquated tech just to be a contrarian. My advice is based on actually reading the thread and trying to understand the problem and the constraints @sikryd is working with.

With all due respect, if you're trying to help, I recommend actually reading what's already been discussed. Some of the discussion and recommendations might make sense to you then. I might not be a total idiot popping off with a backwards idea for no reason. I like new tech. I like electric fans.

"It's not a hard problem" and "it's not longer entertaining" is pretty condescending coming from someone who apparently hasn't read @sikryds posts before implying the recommendation is idiotic.

I guess "It's not a hard problem" if you haven't bothered reading it and just want to pop off with generic advice like "buy $$$$ electrics you can't afford, because they're always better for every situation, always". Yeah, that was pretty easy.

If you really want good gouge on heat management, go to a SYTY forum...(Syclone Typhoon) they run high heat turbos, are GM....and high HP guys use extractors and electric fans....and all the aluminum parts you can shake a stick at.
Again, high dollar cooling systems are not in the budget, hence my recommendation for cheap old crap that works really good, at the expense of some power up top of course.

I'm sure the SY/TY guys know all about cooling constraints, but by now you hopefully know the constraints we're dealing with are completely different. Also, do you think a FI 4.3L V6 (even a hot one) might just dump a little less waste heat in to the cooling system than a carb'ed big block chevy? Oh yeah, and the Sy/Ty platform has a whole bunch more rad surface area than a tri-five..

So yeah, in summary @sikryd could probably go nuts and get a $$$ better radiator, $$$ better electric fans etc. I'll absolutely concede that would be a more elegant solution. But, actually paying attention, he said money was tight, which is why I recommended going back to the stone age with a simple shrouded mechanical clutch fan. It's old tech, inefficient power wise at higher rpms, but you can't beat the cfm per dollar.

But hey, if you have a wiser solution that will double the CFMs for probably under $200, I'm sure @sikryd would like to know about it.

Sorry if I come off a bit salty, but you rubbed me the wrong way implying I'm a fool when you haven't even attempted to read and understand the problem before implying I'm an idiot and offering your own unhelpful advice as the definitive answer.
 
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So...., you don't consider the dual 11" Spal fan with 2720 advertised cfm to even have a chance at being adequate? There's probably hundreds of happy trifive owners that use that fan setup. What fan setup do you use?
 

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sikryd, (wish I knew your first name). I’m not going to get into formulas or convection/ conductivity mind bending stuff. I’m an old school (antiquated) type that’s been through the same sort of BB heat problem before that you’re experiencing now. I’ve also endured the ‘extortion’ problem at one horrible time of my life too, so I completely understand.

All I can say is to try the cheap route first and dump the electric fans for a bit. Keep that setup just in case, but just TRY a good mechanical fan (like a Derale available from Summit) with a cheap plastic shroud. You might be happy just as I was. There just isn’t any electric fan(s) setup that works as good at regular RPM driving level. Just try it man.

Another thought is since price is important go to a Pick and Pull type of source and pull off some likely fitting stuff. Modify things if necessary just for a test. If it all don’t work you aren’t out much from the wallet.

Best of luck to you, and please report back on your findings, regardless of which route you take.
 

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So...., you don't consider the dual 11" Spal fan with 2720 advertised cfm to even have a chance at being adequate? There's probably hundreds of happy trifive owners that use that fan setup. What fan setup do you use?
Apparently not for whatever @sikryd has going on with the big block. All we've got to go on is what he says he's checked already. Maybe there are other problems going on, but all the basics have apparently been checked so that leaves me with 'move more air' as a band-aid.

On my car, I use a crappy stock mechanical, not because it's better, but because my car is a dog with a low output 283 and doesn't need any more cooling. Plus, an electric fan would look out of place on my original old junk.

I actually prefer electric fans though, love 'em!. I don't know why people think I'm crapping on electric fans. Maybe it's because I'm too verbose, I'll try to sum it up in one line.

All I'm saying is a crappy, old school, low tech, power robbing mechanical fan is probably the best solution in this one particular situation to give @sikryd more cooling for very little money.
 

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sikryd, (wish I knew your first name). I’m not going to get into formulas or convection/ conductivity mind bending stuff. I’m an old school (antiquated) type that’s been through the same sort of BB heat problem before that you’re experiencing now. I’ve also endured the ‘extortion’ problem at one horrible time of my life too, so I completely understand.

All I can say is to try the cheap route first and dump the electric fans for a bit. Keep that setup just in case, but just TRY a good mechanical fan (like a Derale available from Summit) with a cheap plastic shroud. You might be happy just as I was. There just isn’t any electric fan(s) setup that works as good at regular RPM driving level. Just try it man.

Another thought is since price is important go to a Pick and Pull type of source and pull off some likely fitting stuff. Modify things if necessary just for a test. If it all don’t work you aren’t out much from the wallet.

Best of luck to you, and please report back on your findings, regardless of which route you take.
Its Jared... I think I am going to try a shroud and mechanical fan because it's like $238 + shipping, which is alot cheaper and faster than any other solution. If it does not work, I can turn around and sell it with my copper/brass radiator. I may pull my headers and have them ceramic coated, but they are such a pain in the ass to get sealed properly, I loathe them. I have to lift the driver's side of the block to get that side out. Just thinking about it gives me anxiety, lol.
 
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