[Formulajones]

Originally Posted by grivera

This - a thermostat is designed to regulate minimum temperature only

Exactly what I explained, you're much better at putting it in fewer words than I am

[Firebob]

That thought is what stopped me from changing it out. I think my next step will be to pull the elect fan and go back to a belt driven. But, of course that puts me right back where I was when it overheated in the cruise lane last year so I'll not stop there. Following that I think the WP is coming off and I'll do some internal inspections of the divider plates and the cooling tubes/rubber cups to make sure everything there is in order.

This engine has probably 5 thousand miles on it. Everything was done so I know it circulates as good as it can. Radiator is new 4 core brass w/waffle core design( whatever that does). Don't know if I would gain anything by going to a big alum radiator but it may be in cards. Does anybody think a pusher fan would help. It'd be an engineering feat to mount one because of the AC core but if it helped I'd make it happen.

Someone mentioned having the right space in between the shroud and the fan tips. I always figured the least space the better. Not so?

[Schurkey]

Originally Posted by Firebob

Someone mentioned having the right space in between the shroud and the fan tips. I always figured the least space the better. Not so?

Absolutely so...as long as there's room for the fan to clear when the engine rocks on the rubber mounts.

Fan half-in, half-out of the shroud is another rule-of-thumb. In some cases, 1/3 in, 2/3 out works even better.

[Formulajones]

Originally Posted by Firebob

That thought is what stopped me from changing it out. I think my next step will be to pull the elect fan and go back to a belt driven. But, of course that puts me right back where I was when it overheated in the cruise lane last year so I'll not stop there. Following that I think the WP is coming off and I'll do some internal inspections of the divider plates and the cooling tubes/rubber cups to make sure everything there is in order.

This engine has probably 5 thousand miles on it. Everything was done so I know it circulates as good as it can. Radiator is new 4 core brass w/waffle core design( whatever that does). Don't know if I would gain anything by going to a big alum radiator but it may be in cards. Does anybody think a pusher fan would help. It'd be an engineering feat to mount one because of the AC core but if it helped I'd make it happen.

Someone mentioned having the right space in between the shroud and the fan tips. I always figured the least space the better. Not so?

Once you get the stock fan and shroud back on, I think the biggest player where you'll see a difference is the radiator. While the copper 4 cores do work well, I've always found an improvement with a good 2 core aluminum that has 1 1/4" tubes in every instance I've swapped them in. I've done that with 3 cars here now and every time there is a cooling improvement.

If you've read the thread I started on my fathers car and the Cold Case stuff he installed, you'll see in there that for years he ran a 4 core copper setup with the stock shroud and clutch fan. That engine would push 190 if you ran it hard on the highway, but would cool to about 175 cruising the back streets.

Fast forward to a few months back when he installed the Cold Case setup, take the electric fan experiment out of the equation. He now runs the exact same shroud and clutch fan on the engine he had with the copper radiator. So basically it's just a radiator swap now with the Cold Case. That thing just won't get hot at all now. 3,000 rpm on the highway and it ran 163 degrees for 15 miles, and as soon as we got off and slowed down to 30-35 mph it actually pulled that engine down to 150 degrees. Just CRAZY what a difference that made. So the radiator alone was worth a good 20-25 degree drop in temps vs the copper he had in it. The only thing that electric fan setup did for it was force it to run 195 degrees all the time, and sometimes push over 200 and never cool down no matter how you drove it, fast, slow, stop and idle, those fans just ran constantly and would never shut off, and wouldn't pull the engine down to a reasonable temp at all.

As far as fan spacing, I never pay much attention to that. I run the factory stuff, and what ever it is, that's what it is. They vary quite a bit from one car to the next. Our 1st gen doesn't have much of a factory shroud on it, and the stock clutch fan just lays in it the way the factory did it, it's more out than in. On our A-bodies the fans seem to be more in the shroud then they are out of the shroud. I'd say it's more like 2/3 in and maybe 1/3 out. It's the opposite of the 1st gen. But it's factory stuff and that's just the way it is. I just roll with it. Never poses any kind of issue at all.

On water pumps, if checking impeller clearance gives you a better feeling, then by all means I'd do it. I never check them, never have in over 30 years of replacing them. I've run them all just the way they show up. I just make sure the rubber seals are replaced and the plate is in good working order. Never had an overheating Pontiac that was related to any water pump issues. I believe you're going to find your biggest changes in the radiator and fan/shroud setup.

[Formulas]

I own 1970 F'bodys and I have one fan shroud that is open at the bottom it does not cool as well as the other that is a solid circle

Both are factory shrouds never tried to science out why the difference

The difference only showed up at higher speeds
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[chrisp]

Originally Posted by Sirrotica

GMB is an aluminum casting with a cast iron impeller, new at Summit $48.68.

https://www.summitracing.com/parts/g...w/make/pontiac

I've had good luck with GMB pumps previously. I used Gates also, but I couldn't find any. They might not be manufacturing them any longer.

Short vane impeller , the all 3 GMB pumps use the same impeller & no difference between the cast iron housing & the 2 aluminum ones they offer / the standard alum. 1 is identical to the HP alum. 1 they sell.

[Firebob]

After years of use one has to wonder about the condition of any used radiator. Stuff settles in and can limit flow through. I believe that a new alum rad would out cool an older brass. Maybe even a brand new brass. Probably a good alum would out cool a brass in the same condition so that is something I'm seriously considering. I'm also not happy with the draw the elect fans put on the motor so if everything's being equal I'd much rather run a belt driven fan so that's the way i'm leaning. But if I get this current setup to do what I want I would definitely learn to live with it.

[Steve C.]

" I'm also not happy with the draw the elect fans put on the motor ...."



From a article about high performance cooling systems in Car Craft magazine.

"Electric fans have become popular with the OEMs because they can move enough air at low speeds to keep the engine cool, relying on vehicle speed to push air thru the radiator at highway speed. This reduces parasitic horsepower losses at highway speeds by eliminating the engine-driven fan. While this may seem trivial, dyno testing in Car Craft resulted in instance of losses of 35 hp at peak horsepower from a simple one-piece, plastic, engine-driven fan. Clutch fans lost between 8 and 19 hp depending upon the clutch model, while a Flex-a-lite Black Magic electric fan driven by the alternator cost 1 hp."

And before anyone cries foul on the statement that the electric fan driven by the alternator cost only 1 hp. Yes, testing as shown there might be a slight decrease in power from the drain from the alternator with electric fans, but it is not the large numbers often thought of. It's nothing to lose sleep over, presuming you have a charging system that is capable of delivering 40 to 60 amps output at low speeds according to articles.

( Information provided in this post does not represent a product endorsement. And unless specified it is not based on personal experience and is offered for general interest only )

Also a important caveat.... these numbers were generated using a 496 hp small-block Chevy at over 6000 rpm. I'll suggest less to be expected on a lower street rpm.





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[Firebob]

Hmm. If you ( and car craft ) says so. I swear I can feel the motor draw down a bit when they come on. Maybe not as bad as I think it is but still.
Here's what I'm saying about the fan size and the area that air is being drawn through the shroud. My core is 23"x17" and the fan draws air through a 15" opening. I'd have to do the math but it's probably Pulling air through less than half of the core area. The rest of the core isn't getting any help cooling circulating coolant at lower speeds when the majority of my issue presents itself.

[Steve C.]

"I'd have to do the math but it's probably Pulling air through less than half of the core area."

And again offered for general interest that topic was approached here in this link. That being the area covered by the fan......

https://www.speedwaymotors.com/the-t...omponent/28863


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[TedRamAirII]

I would be sure that the gaps, all around that shroud are sealed, so that any air that the fan pulls, actually comes through the core, and not around it. Fans pull 20-30 amps, which puts a toll on the alternator, at low speeds. I know if you disconnect the big wire at the alternator, and hook it back up, the idle speed goes down, you cant tell me that's 1 HP. I think its more like 5 with larger amp alternators, more under load.

[Firebob]

That article talks about shroud versus fan with no shroud. Close but not exactly what I'm talking about. I have no proof but I think it may be drawing air flow through the area directly in the 15" path of the fan and not much around the periphery of it thereby losing any benefits that could be gained by flow across the total area of the core. I'm thinking a dual fan setup might be a much better setup for the core size I'm dealing with. One way to find out I guess.

Does anybody know of an OEM dual fan setup for that size ( 17"T X 23"W ) core? I'm sure I could buy a new aftermarket one but I get a deal at the local wrecking yard so it makes sense for me to go there first.

I want to say debating the good and bad with knowledgeable people is really helping me work my way through this issue. In other words whether you know it or not you guys are helping work this out. It's appreciated.

[Steve C.]

That article talks about shroud versus fan with no shroud.

Got it now, sorry for the confusion.


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[Formulajones]

Dual fans on a 17x23 core size would be a pretty small set of fans to fit within those dimensions. Doubt they would move much air.

[Formulajones]

Originally Posted by Steve C.

That article talks about shroud versus fan with no shroud.

Got it now, sorry for the confusion.


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You sent me the same article the other day Steve. I found it interesting how they just removed the electric fan shroud, installed the electric fan directly onto the core of the radiator, and things improved. Just goes to show that a lot of these shrouds designed around these electric fans aren't exactly cutting it.

[Firebob]

I was thinking the same thing about the size of the fans but if you do 15" X 3.14= 47sqin(approx what I have now) and then 2x (12" X 3.14)=75sqin(approx). Seems like quite a bit more surface area getting flow with two smaller fans. As long as they were in a well fitting shroud for the core I think it might make a significant difference. Can't be sure without a trial. But math usually doesn't lie.

[jamaca85]

i bought a summit 30x19 radiator for my 79 firebird. i run the restrictor plate with the med hole in it for a thermostat and a manual 18 inch fan with a shroud. on a 85 degree morning never goes above 180 on the freeway and 195 in stop and go traffic staying around 190 on a constant 30-35 mph cruise. motor is a 40 over 455 with two sleeves. i also have no heater in the car so i have the water port blocked at the timing cover and i connected the the heads in the rear to circulate the coolant in the rear of the heads. i think its all the the radiator you choose and fan and shroud set up.

[Firebob]

Last night I went out and lowered the temp settings I had on the fans. Low on at 180/off at 175. High on at 185/off at181. Now just need some hot weather and some time to take for a test ride. Would be something if something that simple makes the difference. I'm not holding my breath. Think I had the high set to come on at 195 before and it went to 206 in the heat. So better than 10 degrees higher anyway. I'm not holding my breath. That would be a very thin thread to hold onto to expect it to operate correctly under extreme conditions.
I'm still thinking dual 12" fans in a well fitting shroud may be in the near future.

[Steve C.]

Regarding that electric fan driven by the alternator that cost 1 hp.

Don't shoot the messenger, I'm only presenting what the magazine article stated And keep in mind the testing was at a high running RPM and not at idle.

I made an attempt to find a copy of Car Craft issue to read more about the testing but couldn't find it. However based on the information at the time I interpret it that they hooked up the electric fan directly to run off the alternator on the motor and thru dyno readings the draw on the alternator from the electric fan resulted in a 1 hp loss at peak rpm. The results will vary.

Related, in Circle Track magazine they did dyno testing to determine the benefits and draw backs of running with and without an alternator. The goal for attaining maximum power by some teams is to run without an alternator. Note, the primary focus was on the more popular capacitive discharge system (and included a electric fan) and how it is affected as the battery voltage becomes low. As here a result of the testing they stated the removal of the alternator was worth only 2 or 3 horsepower.



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[Sirrotica]

The first time you spin out on a dirt track and the car stalls, but the battery is too weak to restart it, and other cars are bearing down on you, those 2-3 HP mean nothing...……………..LOL

I always ran an alternator on my own race cars, but have been involved with other cars that didn't.

I've been following this thread, but I really don't see how an electric fan can get the same amount of work done at potentially 30 times less energy than a mechanical fan can. It must be the new math I'm not getting...……..

The idea has been thrown out there that the car manufacturers changed over for fuel mileage reasons, but until engines were mounted transversely in a chassis, very, very few cars had electric fans. Obviously there is no way a mechanical fan can be driven by the conventional transverse mounted engine so enter the electric fans.....