To use or not to use pusher fan?? - ClassicOldsmobile.com


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Old July 10th, 2018, 01:20 PM   #1  
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To use or not to use pusher fan??

Hello Everyone.
'71 442 455. 4K miles on rebuilt (peppy motor). I do not have specs on it.
I bought a Flex-A-Lite Trimline Electric Fan# 116 to put in front of the rad/condenser as well as the 7 blade factory fan.
I want to get some opinions before installing.
I have been told they block more air then they can push. (not sure I believe that).
I assume this can't hurt.
With the outside temp in the low 90's and with the A/C on, engine temp is around 215. if the lights are long, then it gets to 225.
The "non-Hot" hours it runs 180/185.
Here is what I have done:
System has been flushed.
Factory radiator - not recored but clean and flowing well.
7 blade Factory fan
New fan clutch
160 degree 'stat
New 16lb radiator cap.
Waterwetter
50/50 mix of antifreeze/water
Shroud is perfect.
Rubber seals around radiator and shroud are in place.
Advanced timing.
Richened the carb.
New belts and hoses. Lower hose has spring in it.
Condenser and Radiator fins are cleaned and blown out.
Tried running non-ethanol gas, no noticeable change
Underhood insulation

The fan clutch is 1.5 inches from the radiator. The farthest edge of the fan blades are 2.5 inches from the radiator. The fan sits inside the shroud .75 inches.

thanks!

Last edited by rick442; July 10th, 2018 at 03:09 PM.
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Old July 10th, 2018, 02:13 PM   #2  
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I have had both at one time or another... I prefer pullers. I had a pusher setup in my 66 Corvette that was ineffective. I changed to a puller and created a noticeable difference in cooling ability. My 1968 442 w/468 CID had an aluminum radiator with twin Spals with no fan blade... never had any cooling issues on 90 degree days here in the Nashville area. JMHO, others may have different experiences.
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Old July 10th, 2018, 02:36 PM   #3  
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it makes sense that pulling air through the rad and through a shroud will flow through more rows and cleaner through the radiator. Even blade design plays a part in it. Some of the best fan assemblies are removed for the bone yard and applied to older vehicles.
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Old July 10th, 2018, 02:43 PM   #4  
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You've got a good list of items that affect cooling checked off!

Do you have the factory four blade or 6 blade clutch fan?

How far does the fan fit into the shroud?
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Old July 10th, 2018, 03:10 PM   #5  
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Ah, I forgot about the fan clutch. I had bought a new one and just modified my post.
the fan clutch is 1.5 inches from the radiator the farthest edge of the fan blades are 2.5 inches from the radiator. The fan sits inside the shroud .75 inches.
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Old July 10th, 2018, 05:36 PM   #6  
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That all sounds good too... I got nothin
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Old July 10th, 2018, 06:02 PM   #7  
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Quote:
Originally Posted by rick442 View Post
Hello Everyone.
'71 442 455. 4K miles on rebuilt (peppy motor). I do not have specs on it.
I bought a Flex-A-Lite Trimline Electric Fan# 116 to put in front of the rad/condenser as well as the 7 blade factory fan.
I want to get some opinions before installing.
I have been told they block more air then they can push. (not sure I believe that).
I assume this can't hurt.
With the outside temp in the low 90's and with the A/C on, engine temp is around 215. if the lights are long, then it gets to 225.
The "non-Hot" hours it runs 180/185.
Here is what I have done:
System has been flushed.
Factory radiator - not recored but clean and flowing well.
7 blade Factory fan
New fan clutch
160 degree 'stat
New 16lb radiator cap.
Waterwetter
50/50 mix of antifreeze/water
Shroud is perfect.
Rubber seals around radiator and shroud are in place.
Advanced timing.
Richened the carb.
New belts and hoses. Lower hose has spring in it.
Condenser and Radiator fins are cleaned and blown out.
Tried running non-ethanol gas, no noticeable change
Underhood insulation

The fan clutch is 1.5 inches from the radiator. The farthest edge of the fan blades are 2.5 inches from the radiator. The fan sits inside the shroud .75 inches.

thanks!
I did all of the above, and had your temps with the a/c on, I finally installed a Dewitt aluminum radiator with 2 puller fans, my temp was no more than 200* on the Power Tour, I hated to move away from stock, but wanted decent temps while running my a/c. I still have the stock shroud, so the engine compartment still looks stock
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Old July 11th, 2018, 12:38 AM   #8  
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A pusher pushes a lot lot more air through a radiator, than they can suck through, unless you have a full shroud properly fitted for the puller. Nice electric fans that move a lot of air are great, but maybe even greater is using the largest surface area aluminum radiator can make a world of difference. This increases cooling dramatically even with little to no air flowing through other than by convection. Aluminum is much better than brass at cooling, and more surface area as well makes them really good. A 50/50 mix of antifreeze and tap water or soft water are the best, to cool and keep down corrosion. Never use distilled watter unless you like electrolysis. I was absolutely amazed at the difference a little larger aluminum radiator had over my brass radiator, even without a fan installed on it yet. It was spooky and cold on the temps.
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Old July 11th, 2018, 05:43 AM   #9  
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Please elaborate on your electrolysis comment and how tap water stops it.

As for the main issue, a good test is to see what is going on at different times. It sounds like the car heats up at idle, does it heat up while driving? The old saw of overheating while idling is an airflow problem, overheating while driving is a coolant flow problem. If you have both, a new water pump or a better or recored radiator may be in order.

Airflow is not intuitive, and many "car guys" think they can "makes sense" it. If you stack two fans on top of each other, it is a negative result. If you have a radiator and condenser in between them, it can still be negative as a radiator and condenser are not stators (which is a stationary air flow device between rotors, ie, fans, in things like turbine engines.)

Also, assuming the gauge is accurate, those temps are not bad, and can even be considered normal. Fan may be too far in the shroud, check factory specs.
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Old July 11th, 2018, 06:30 AM   #10  
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It all about the ions.




In the old days where everything was the same metal not much of a problem, but when flowing water through say iron and different metals you are creating a battery situation. And while batteries love distilled water they hate hard water.



And here is more on antifreeze from Scotty Kilmer, and old versus new.



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Old July 11th, 2018, 07:07 AM   #11  
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"....It all about the ions....."

It's actually all about fluid dynamics and in this common case, aerodynamics. Very few give adequate thought to the real problem the exit of the now very heated air from the engine compartment presents, which is where a large part of the cooling solution is found. Moving air through the radiator better or worse ways doesn't mean as much if the hot air cannot exit the compartment (usually when the vehicle is stopped) in great enough measure as a part of the solution. In this light the large engine driven fan/shroud is just about without parallel in the design of the vintage of our vehicles for this task.

A tightly closed and fitted hood, well sealed front wheel houses, and today's more popular tighter ground clearance all mean the heated air must be forced from the engine compartment. Guys who have run without a hood or have a hood with holes for various reasons have known forever how little fan you actually need even in the hottest weather when the heated air can simply escape upwards and out when at slow speed or stopped. So my opinion is unless you know the coolant moving through whatever radiator you have is not seeing adequate air to liquid heat transfer due to a radiator airflow problem or perhaps too fast a coolant flow through the radiator for a given cooling airflow, the solution may lie in other considerations. GM never really solved this idling overheat issue in these years, Cadillac and Corvette cars started to include aluminum radiator cores and fuel returns to prevent running vapor lock even in the days of fuel formulated to remain liquid at 7psi fuel pressure in extreme heat situations.

The wetting agents help no matter what the other considerations might be, cost considered, but are no final solution.

I had a 1969 Corvette 427-435 which my brother has now. That car would overheat very quickly in any stopped traffic or slow moving traffic with all system parts in good condition. The rear facing hood was a godsend, you would just reach down and pop the hood to safety latched position, opening the rear of the hood about 4", raise the idle slightly, right back to 180 in moments. No such luck with most of our cars, although my 1964 98 gasser has no front wheel wells, never overheats regardless of any situation.

If you can't stand next to your car idling hot on a hot day and feel the hot blast of air exiting the underside of the car by the door on either side, look for air flow problems out of the engine compartment as the main part of your solution, engine driven or electric fans, whatever else may present itself.

EDIT: Food for thought reading.

https://en.wikipedia.org/wiki/Meredith_effect

Last edited by coldwar; July 11th, 2018 at 07:36 AM. Reason: spelling
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Old July 11th, 2018, 07:39 AM   #12  
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"....It all about the ions....."

It's actually all about fluid dynamics and in this common case, aerodynamics. Very few give adequate thought to the real problem the exit of the now very heated air from the engine compartment presents, which is where a large part of the cooling solution is found. Moving air through the radiator better or worse ways doesn't mean as much if the hot air cannot exit the compartment (usually when the vehicle is stopped) in great enough measure as a part of the solution. In this light the large engine driven fan is just about without parallel in the design of the vintage of our vehicles for this task.

A tightly closed and fitted hood, well sealed front wheel houses, and today's more popular tighter ground clearance all mean the heated air must be forced from the engine compartment. Guys who have run without a hood or have a hood with holes for various reasons have known forever how little fan you actually need even in the hottest weather when the heated air can simply escape upwards and out when at slow speed or stopped. So my opinion is unless you know the coolant moving through whatever radiator you have is not seeing adequate air too liquid heat transfer due to a radiator airflow problem or perhaps to fast a coolant flow through the radiator for a given cooling airflow, the solution may lie in other considerations. GM never really solved this idling overheat issue in these years, Cadillac and Corvette cars started to include aluminum radiator cores and fuel returns to prevent running vapor lock even in the days of fuel formulated to remain liquid at 7psi fuel pressure in extreme heat situations.

The wetting agents help no matter what the other considerations might be, cost considered, but are no final solution.

I had a 1969 Corvette 427-435 which my brother has now. That car would overheat very quickly in any stopped traffic or slow moving traffic with all system parts in good condition. The rear facing hood was a godsend, you would just reach down and pop the hood to safety latched position, opening the rear of the hood about 4", raise the idle slightly, right back to 180 in moments. No such luck with most of our cars, although my 1964 98 gasser has no front wheel wells, never overheats regardless of any situation.

If you can't stand next to your car idling hot on a hot day and feel the hot blast of air exiting the underside of the car by the door on either side, look for air flow problems out of the engine compartment as the main part of your solution, engine driven or electric fans, whatever else may present itself.

When you are fighting a borderline heat problem you use tricks like you mentioned, and they do work. An old trick was spacers under the hood, at the hinges, so the back of the hood was now open. A big hood scoop hole in the center of the hood obviously helps. Done them all. But I consider electric powerful pusher fans and the largest surface area aluminum radiator you can get in there much more powerful, and this comes from years of real world daily driver, with a 455 in the tiniest engine compartment of a 70s Toyota, in the hottest desert heat daily driven in town. No belt driven fan possible. The water pump pulley bolts are less than inch from the core, and the pulley less than a foot from the hood.


Th Corvettes were never designed for slow speed or big power. They needed a much bigger radiator and frontal air flow, for that and didn't get it. Now, block air flow even more with AC condensers and they became a real nightmare after a short period of time, as what cooling they did have dropped with corrosion and the drop in efficiency.
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Old July 11th, 2018, 08:19 AM   #13  
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The passage of time has caused me to forget another very important consideration in hot weather operating, specifically with bored BBO engines, that is, fuel quality.

When fuel quality for a given C.R. allowed something like 16 lead timing and the engine would still start when hot, perhaps with a kill button to short ignition until engine is spinning, was a big part of hot weather operation with these engines. If you have to pull it back to 8-10 your engine is not only going to run a lot hotter overall, but will overheat faster regardless of conditions. I aready know I can run Shell V-Power 93 octane with 14 and 9:1 on a unrebuilt 1972 U-code 455. In the past it was 100 octane or nothing, almost always avgas-pump gas mixes, usually 30/70. The Oldsmobile combustion chamber likes lead in the timing, to a practical limit of no further gains in power. Still a lot better then a SBC wedge.
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Old July 11th, 2018, 09:37 AM   #14  
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Thanks Everyone,
I'll install the pusher next week sometime and keep everyone posted. At minimum, the outcome will give us more data.
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Old July 11th, 2018, 11:05 AM   #15  
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Thanks Everyone,
I'll install the pusher next week sometime and keep everyone posted. At minimum, the outcome will give us more data.

I don't know if you are use to installing electric fans but a common mistake is wiring them backwards from what ya want. To test this wire it direct power and put your hand on the other side of the radiator from it, to make sure you feel the air blowing through the core. For a puller fan you do the same but you down want to feel the air rushing trough since its going the wrong way. At idle it will cool that way but not when you get up to speed. As the air trying to blow out from be wired backwards and the air flow from moving in stalls or cancels it out. JFYI Happy playing
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Old July 11th, 2018, 11:10 AM   #16  
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I installed an after market aluminum radiator in place of a re cored factory 4 core radiator.

The aluminum radiator dropped the operating temperature down to 180 degrees, no matter how hot it is outside.

Factory shroud, rubber seals, 6 blade fan with clutch, 180 high flow thermostat.

A hand held temp gun shows about 175 to 180 degrees at the thermostat housing after a 1 hour drive.
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Old July 11th, 2018, 11:40 AM   #17  
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I have an aluminum radiator, all the shrouding and a factory 7 blade fan and thermal clutch. On the hottest days it runs 175-180 sitting in traffic, turn on the air and it may go 195-200, once again in traffic or idling. This is also a stout 455, with a TH400 and loose converter. Im normally a big fan (ha!) of keeping factory engineering, but given the choice of old school copper/brass radiators or modern aluminum, the new stuff wins hands down.
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Old July 11th, 2018, 12:03 PM   #18  
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I have an aluminum radiator, all the shrouding and a factory 7 blade fan and thermal clutch. On the hottest days it runs 175-180 sitting in traffic, turn on the air and it may go 195-200, once again in traffic or idling. This is also a stout 455, with a TH400 and loose converter. Im normally a big fan (ha!) of keeping factory engineering, but given the choice of old school copper/brass radiators or modern aluminum, the new stuff wins hands down.

My view is the same, also with the large electric pusher fans over the factory fans and shrouds. More room up front and a lot safer without spinning metal blades. A lot quieter most of the time with the electrics off, and more horsepower and mileage. Now a days, it can be even better with fan controllers where you can set when they come on for temps, and how fast they will turn. Very trick.
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Old July 11th, 2018, 04:04 PM   #19  
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Get rid of the electric fans and move your factory fan so that it extends about 3/4 to 1 inch outside the fan shroud. With the fan totally inside of the shroud, you are recirculating hot air around the outer edge of the fan.
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Old July 11th, 2018, 05:11 PM   #20  
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....but given the choice of old school copper/brass radiators or modern aluminum, the new stuff wins hands down.
Just so everyone is on the same page, aluminum radiators are nothing new, or even modern. The only hold back for a wider use is (was) corrosion and metal fatigue. All liquid cooled WWII aircraft used AL radiators for their size performance efficiency gains but also for weight savings, a benefit for us also. High performance cars used AL before and since up to today. Reliability has come a long way due to researches, my 1996 Aurora had its original AL radiator at 200k miles. Aluminum core OE cross flow GM radiators were sought after in the 70's and 80's, but were not common in yards or at a scalpers price. Now since Harrison and Modine no longer make the original type core material correct for the cars being discussed here, today it's either more flimsy mexican brass/copper core material and tank material or AL.
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