[Steve C.]

"In 1970 Pontiac added a top air deflector to AC Cars on Firebirds and others to help pull only out front air into the radiator and condenser."

https://www.classicindustries.com/product/f259.html


.

[Mike Fowke]

Originally Posted by Stripes

I had no issues before the heat load of the AC was added. And its still ok when the car is moving... Can your car idle endlessly without overheating in 100F weather? Can the fans keep up?

They're keeping up in traffic so far, but we haven't seen 100 yet. I did an auto-cross July 25th with no issues. It was 90 and humid. When I put the Spals and new shroud on in May l let it idle in the driveway for 20 minutes or so. It never went above 180.

As you probably know, the shroud is a big part of the cooling efficiency. I can feel air pulling through the core about 8" in front of the radiator, but I don't have a condenser. My shroud covers and seals the entire core and is an inch deep. I had a local fab shop make it.

I talked with Mahaffey about their shroud and fan, but it wouldn't fit with my vacuum pump. You might give him a call before you pull the trigger on the Flex-A-Lite. http://www.mahaffeymotorsports.com/FanShrouds.htm

[Formulajones]

I've never had a problem with the stock clutch setup and original shrouds. My 454 chevelle is factory AC. Stock clutch fan and shroud. Living in AZ cooling is a must, and we've seen plenty of days well over 100 degrees lately, but that's typical every summer.
With AC running on the Chevelle it would settle in at 190 at an idle and never go above that. Once moving it would hold about 185, there really wasn't much fluctuation. Without the AC in this heat it'll run 175 on the highway (3,000 rpm) it actually run cooler when idling or slow moving in traffic, it will drop to 165-170. So it actually runs cooler at slower speeds. I run a 160 stat, it has factory AC pulleys that move the pump faster, and I use a Griffin aluminum radiator in it. Timing and fuel have to be correct, and how vacuum advance is dialed in is a big player. For a 600 hp engine I can't complain.

We went through the whole electric fan experiment with dad's 571 ci Pontiac. He runs a Cold Case radiator in it. Dual electric fans were probably the worst thing we could have done. The car ran hotter everywhere, idle, at speed, didn't matter, it would just stay at 190 and never come off.
Went back to the stock shroud and clutch setup and it acts pretty much identical to my chevelle. The slower he drives the cooler it runs. On the highway the other day it was just over 100 degrees outside and the Sniper said he was holding steady at 178 degrees cruising at 2800 rpm. When he gets off the highway and cruises at 25-35 mph, or even sits and idles, it comes down to 165 within a couple minutes. This engine makes 724hp so for it to run as cool as it does in the AZ heat I'm not complaining and have no interest in changing it around anymore.
I do like how electric fans clean up the engine bay though. If it were me, I'd be working on getting the stock setup efficient, checking the air pathways, making sure the clutch works properly, check pulley ratios, most of all making sure the timing is adequate for idle and low speed situations where you're having your heat issues. Best of luck with what ever you decide.

[RocktimusPryme]

If your engine at long sitting still times is overpowering a 180* thermostat over time I dont see how putting a 160 in will help. It buys you some more time maybe, but if its going to get to 230* in heavy traffic with a 180 its going to do the same with a 160 is it not?

FWIW, my 67 has a stock repro shroud but a long nose 69+ water pump. So it sits closer to the radiator than it should by a half inch. I bought a shorter clutch to try and offset this.

[Formulajones]

Correct, a 160 just buys more time.

From what I've found if sitting idling and getting hot it could be one or a combination of things. Pulley ratio, clutch, or maybe the shrouding isn't complete or missing a component around the core support, very lean idle mixtures, and the biggest player I've found is very little timing, either low mechanical timing at idle or not enough vacuum advance or both.

[shoebox1.1]

On our chebby hot rods we’d get a wrecking yard fan off of a 3.8 mercury sable. Large diameter single. Dirt cheap and has an integral Shroud Always cooled hot cars. Of course. Seal the radiator sides to the core support, air dam in the front if possible. Electric water pumps with restrictors always good too.

[shoebox1.1]

And then switch to aluminum heads. That always drops temps

[RocktimusPryme]

Originally Posted by Formulajones

Correct, a 160 just buys more time.

From what I've found if sitting idling and getting hot it could be one or a combination of things. Pulley ratio, clutch, or maybe the shrouding isn't complete or missing a component around the core support, very lean idle mixtures, and the biggest player I've found is very little timing, either low mechanical timing at idle or not enough vacuum advance or both.

I dont think any of those are my problem. I have a wideband. If anything im a little rich. I have the upper baffles for AC cars, a nice radiator, big fan and a shroud. Timing is about 36* all in with vacuum advance hooked up.

Im REALLY hoping to find a smoking gun when I pull the water pump. Like a big gap between the plate and turbine.

[Formulajones]

Originally Posted by RocktimusPryme

I dont think any of those are my problem. I have a wideband. If anything im a little rich. I have the upper baffles for AC cars, a nice radiator, big fan and a shroud. Timing is about 36* all in with vacuum advance hooked up.

Im REALLY hoping to find a smoking gun when I pull the water pump. Like a big gap between the plate and turbine.

Where is the timing at idle and low speeds? I'm guessing your vacuum advance is running ported?

Contrary to popular belief an efficient running engine with a happy combination can still benefit with a little more initial timing and vacuum running off the manifold.

[RocktimusPryme]

Originally Posted by Formulajones

Where is the timing at idle and low speeds? I'm guessing your vacuum advance is running ported?

Contrary to popular belief an efficient running engine with a happy combination can still benefit with a little more initial timing and vacuum running off the manifold.

Its hooked up to manifold right now, adding about 12* at the crank IIRC.

But I have done both, no notable difference. The only thing that made a real difference was the going from an ebay special aluminum job to the COld Case. Lowered temps by about 15 degrees when moving.

Also of note for anyone reading this. I switched from a standard style parts store T-stat that was rated at 170. Seemed like it came on more like @190. Switched to one of the high flow designs. Car runs dead on its rated 180* now when moving. The extra money is worth it to trust the rating.

[Formulajones]

What I generally do here is run anywhere from 14 to 18 initial depending on the car. Both examples I mentioned above are at 18 initial. I have another 10 added with vacuum advance, making sure the vacuum advance is sensitive enough to activate fully or near fully with the idle vacuum those engines produce.. So both of those cars sit and idle around 28 degrees of timing.

Laboring the timing low with 10-12 initial and no vacuum advance definitely heats those cars up in traffic or at idle. It's a large part of the reason why dad's 571 making the power it does, actually runs cool at idle and slow speeds.

I found the same thing with our Z. It's also 18 initial and another 10 added with vacuum that is all in with the vacuum the engine makes at idle. Not only does it help to tame the 254 @ .050 cam in the little 302 but I can switch the vacuum back and forth from ported to manifold and drive it a few days, it's routinely 10 degrees hotter with ported vacuum at slow speeds and sitting still.
It's also part of the reason that little engine with that big camshaft can loaf around town in 5th gear at 35 mph and pull the car around without barfing and coughing. Making it a pleasure to drive, while others with little 230 cams in big 455's can't seem to go slower than 60 mph in overdrive.
There are a bunch of reasons I set them up this way. Not because they need it, but it helps in so many areas of drivability. It's this along with a combination of everything else everyone is talkin about that works together to keep these temps in a zone.

I understand the frustration though and see it all the time. Every time we go to Goodguys and 2,000 cars try to funnel out of that place, there are always several dozen that puke antifreeze before they can get out of the lot, and that's when it's only 85 degrees outside, lol. I don't know how those guys survive when it's over 100. I guess they just don't drive them. I don't have that option.

[RocktimusPryme]

Originally Posted by Formulajones

I understand the frustration though and see it all the time. Every time we go to Goodguys and 2,000 cars try to funnel out of that place, there are always several dozen that puke antifreeze before they can get out of the lot, and that's when it's only 85 degrees outside, lol. I don't know how those guys survive when it's over 100. I guess they just don't drive them. I don't have that option.

For me the frustration is that I really feel like I did everything right here. The one caveat being I didn’t install the water pump. Lots of people report a factory style setup with a big clutch fan works great. I’m still experiencing issues with long periods at idle.

If there isn’t a smoking gun with the water pump I don’t know what else to do other than electric. Pulley swap maybe.

My setup is likely close to what you describe. I think I’m more at 24-26* at idle but it’s been a minute since I set it up. I think I’m at 12-14 on the crank mechanically and then have the vacuum on manifold.

[Formulajones]

Originally Posted by RocktimusPryme

For me the frustration is that I really feel like I did everything right here. The one caveat being I didn’t install the water pump. Lots of people report a factory style setup with a big clutch fan works great. I’m still experiencing issues with long periods at idle.

If there isn’t a smoking gun with the water pump I don’t know what else to do other than electric. Pulley swap maybe.

My setup is likely close to what you describe. I think I’m more at 24-26* at idle but it’s been a minute since I set it up. I think I’m at 12-14 on the crank mechanically and then have the vacuum on manifold.

Sounds like you've covered the bases.

I can't remember the brand water pump on dad's engine. It's an aftermarket mechanical pump, not a stocker. I'll have to look at it.

On the chevelle I just run a cheap reman GM pump that I install a plate on the back of the impeller myself (old school trick)

[android 211]

I thought my GTO ran hot as once warmed up the factory temp gauge was at 3/4. An IR gun showed it was running around 190 200 and I live in Florda.
On another BB car I had a six blade fixed paddle fan and shroud and the car ran hot at low speeds. I swapped in a 7 blade clutch fan and a new Hayden clutch and temps went down about 10-15 degrees so i called that a win.

[389]

We just had a long session on this one, I talked with two retired GM engineers they both agreed, the big 8 blade clutch fan, fully engaged, pulls 9,500 cfm @ 1800 rpm. The electric is not even in the same block let alone ball park... You car argue all you want, there is no way the electric is anywhere near the clutch but some people love to argue. I like to adjust the bi-metal so it doesn't take too much power to run..

[Formulajones]

I don't see people arguing, it's just a discussion. But I do believe there are applications where electric fans have their merit.

I've tried them on a couple of different street driven cars and I've come to the conclusion, for me, that I just prefer the mechanical fan setups for simplicity, reliability, and I've had better cooling success with them as well.

Doesn't mean people shouldn't try it though. Some may have better success than others.

[RocktimusPryme]

You can call me argumentative if you want, but I would say that number is tough to believe. One, I don't think Ive ever seen a clutch fan with more than 7 blades on a muscle car. Even if you nerfed that number a little for the big 7 blade fan many of us run that number would be very tough to believe. Seems like it would be impossible to overheat if the fan moved that much air. Yet here we are. People with clutch fans, talking about running hot.


If the clutch fans were THAT amazing at low RPM, I don't think so many people would run electrics. You could run it however you want, no shroud, dinky radiator, doesn't matter, and that is clearly not the case.

[Formulajones]

And to be fair to the electric fans, there are big differences in quality, the fans themselves, the shrouds they are designed with etc..

There are a lot of good electric fans out there, OE and aftermarket.

My 88 Iroc had factory electric fans, I later switched them over to a pair of LS fans, they worked flawless on that car. As well as 4 4th generation Camaros we had, all with electric fans, and all these cars are bottom feeders too, meaning they grab air from under the front bumper. All of those worked well, and of course that's OE engineering.

I even swapped an LS into a 72 blazer and used LS electric fans. That worked okay but found even that setup would start getting warm when moving slow for a long period of time. Not what you would expect from electric fans.

The aftermarket stuff is where success is all over the map. Different designs, fans, shrouds, motors, dual vs single.

I tried aftermarket dual fans with a shroud on dad's GTO and that was a total loss all the way around. It never cooled well at idle or on the highway, and I attribute most of that to a poorly designed shroud. Even though it encapsulated the entire radiator core, it limited airflow through the assembly to just the fans themselves. So even at speed there wasn't enough air flow getting through the core and the engine would get hot. It wasn't really any better at cooling sitting still either. Tried 3 different controllers, cutting relief holes with rubber flaps in the shrouds, all the tricks people mention. It just wasn't cutting it. Tired of messing with it I switched it back to the stock clutch fan and shroud and now you can't get that thing even remotely hot. I believe the biggest reason for that is the huge by giant factory shroud that promotes very efficient airflow through the radiator at all times, rather than a squared off piece of sheet metal that only sat an inch off the core with no way out for the air to go.

[Steve C.]

A fwiw.....

International Harvester 8 blade mechanical fan rated for 9,500 cfm @ 1800 rpm



.

[RocktimusPryme]

Im not going to say I put a ton of work in, but a quick google search for "International Harvester 8 blade mechanical fan" did indeed lead me to a big 8 blade clutch fan for an international that I may admit would move quadruple what good electrics are rated at. It was also 26" in diameter. So i would have a hard time adapting it to my Firebird.

I would like to see someone else do it though. Would be an interesting hood scoop lol.

In all seriousness. I guess I shouldn't say I don't believe that one is rated that highly. But differences in CFM ratings as noted early are notoriously different. But just from a physical standpoint, surface area and pitch of blade in ability to move air. I cant imaging that big clutch fan could possibly be 3 to 5 times better than an electric or dual electric. Somebody is playing funny business with numbers at that point.