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Is there any reason I can't run an electric fan from in front of the radiator instead of behind it? I bought a much thicker radiator for my '54 and put a Firebird front clip on it and I am getting ready to build a radiator mount and need to decide the best way to do it and mount the fan.

They can be mounted as either pullers or pushers. No problem!🛠

Thanks. I've never seen one done that way, so I was wondering if there is a reason. On the stock set up, the stock fan would not fit with the new radiator.

Some fans can be either pusher or puller. Usually, maybe always, the pusher move less cfm though.

Dennis

Pulling the air is quite a bit more efficient.

When I start building the brackets, I guess I will try harder to make it pull.

Agree.

On a somewhat related note, I had an old 48 Ferguson TE20 tractor, bought it from a fellow that had it about 75% restored but that was good enough for what I used it for. But after about an hr of brush hogging it would start to overheat and I'd have to shut it down for 20-30 minutes to cool off before I could finish the field.
One day the water pump started leaking and I swapped it out. Thats when I discovered that the fan was turned backwards so it would blow back through the radiator out the front grill. I later was told alot of old timers did this to keep the grills from clogging up. I turned it around to the proper direction and the tractor never overheated again.......

Turning a fan around 180 degrees will not reverse the air flow. It will however greatly reduce the amount of air it will pull. This is due to defeating the action of the airfoil action of the curve along the length of each blade.
The same thing occurs when you put an outboard motor in reverse. It makes all of the noise of going fast when you goose it, but it doesn't pull the boat back very fast.
Carl

Putting the fan in front is called "a mistake", only do it if there's no other way.

So a friend of mine is adding one to the front of the radiator on his old Pontiac. To change it to a pusher the instructions say to reverse the fan blade and also the polarity of the supply. It mounts through the core with special plastic retainers.

I put a 1300 cfm puller in front of my radiator since my new radiator was to thick to keep it stock. Ensure that you wire through ignition switch so it turns off. Also, get sensors to turn it on automatically when it hits whatever temp you pick. I am happy with what I have, but have not driven it extensively due to working out the bugs.

Chris

Absolutely nothing beats a belt driven fan. I'd go to a great deal of effort to avoid having to use an electric, even if it meant redesigning the radiator mounts to create enough space for an original equipment type fan blade on the water pump.
Jerry

puller in front of my radiator

Backward: pusher in front, puller in back

The difference (besides any efficiency, blade direction, blah): the front-mounted pusher fan is an OBSTRUCTION to natural air movement at cruising speed - the car would be better off without it.

That makes good sense to me. You will be reversing direction, and retaining the proper orientation of the curves in the blades. Having said that, the blades on that setup must be specifically designed to accomplish this swap. It wouldn't work with a blade designed like an original fan or a standard flex fan.

I did just that on my '49 to accommodate a 350. I modified the bottom of the radiator support to allow the lowering of the radiator to put the belt driven fan in the center of the radiator, as well as creating fan blade clearance for the transmission cooling lines. I added an original fan shroud from a '49 big truck engine.
It works so well that I can't run the truck anywhere near the front door for fear of sucking all the sheets through the keyhole.

I openly admit I'm NOT an expert but I fail to understand why a pusher is less efficient than an puller. All fans both pull AND push depending on which side of the fan you are on while it's running. Someone explain.

The motor and the support structure of a pusher fan effectively blocks, or at least deflects airflow to part of the radiator core. At highway speed where the fan could be eliminated altogether without any adverse effect on cooling, that reduced swept area of the core is likely to cause a slight, but noticeable reduction in the efficiency of the cooling system. Puller fans work better because they don't interrupt the airflow over the core as much.
Jerry

"The difference (besides any efficiency, blade direction, blah): the front-mounted pusher fan is an OBSTRUCTION to natural air movement at cruising speed - the car would be better off without it."

Panic,

It seems that air conditioned vehicles have condensors mounted to the front of the radiator that reduce the airflow through the part of the radiator behind the condensor more than a pusher fan would. Yet, when I added AC to my 1971 Dodge van 20 years after I bought it new without AC the temperature gauge did not indicate that the engine was running any hotter. That seems counterintuitive but it's hard to argue with a gauge. That old van is still going strong and even pulling a travel trailer at age 46 and about 355K miles. It's hard to beat the durability of old school Detroit iron.

It's generally agreed that pusher fans are less effective than pullers and I'm really curious why that is. In addition to an AC condensor some vehicles have even more obstructions like transmission coolers and even power steering fluid coolers in front of the radiator yet they have no overheating problems. So it appears that placing other cooling devices in front of radiators doesn't keep them from working effectively. How that can be is curious.

I understand restriction but any restriction is there whether the housing and support structure is on the front or back of the radiator. Open a window in your house then put a board over it. It makes no difference whether the board is on the inside or outside, the air is restricted the same.

"I understand restriction but any restriction is there whether the housing and support structure is on the front or back of the radiator."

Tiny,

That seems like common sense but there must be a reason why fans have proven to be less effective in "pusher" mode.

In my work as a geologist I'm often around big earth moving machines like bulldozers. At least before the days of enclosed cabs their fans were mounted to the fronts of the engines but the blades push air forward through the radiators, presumably to keep that hot air off the operator. I don't know if that factoid clairifies or further confuses the issue.

Googling the issue I found a lot of claims that pulling is more efficient but universally I found no attribution of proof, only repeating what they'd heard someone else say. I did find one site for engineers apparently where the claim is just the opposite. <CLICK>

Tiny,

Thanks for posting that engineering info. Here's what fan manufacturer Spal has to say regartding push vs. pull: https://www.a1electric.com/spal/faninfo.htm. But as you point out they don't give any back up data. You'd think they know since they make the things

If this subject of cooling improvements interests you, you might enjoy seeing what the factory optional fan shroud for my '36 Chevy PU looks like. It's not like what is used today but it definitely works. I could send you a photo if you like.

Nope, I'm not that interested in the details of engine cooling. What caught my attention is what I noted in my first post, the claim that one direction is more efficient than the other when every fan does both, push and pull, at the same time, no matter the mounting placement. It makes no sense to this layman. Could there be validity to the claim? Certainly, just like the engineers say about turbulent air from a pusher cooling better, that's not an obvious trait to the layman so I wouldn't have thought that either. It's entirely possible that a puller IS more efficient but at this point I see no reason to believe it. I'm not a machinist, I'm not a scientist but I am fairly comfortable with how things work in a general sense. I'm a natural born skeptic & if something pegs my skepto meter you'll need to prove it to me.

Sitting here in my deck swing enjoying a cup O joe I looked over at my heatpumps outside unit and observed that the fan mounted on top pulls the air through the coils then up & out,similar to an auto's fan. I'm no mechanical engr, but I'd swag that this orientation causes the air moving through to contact more of the heat exchangers surface than if the fan pushed air down from the top out out through the coils.
My thesis is such, with the fan being a puller, it causes the entire inside area of the coils to become a low pressure area. I think one of the rules of thermo dynamics is air cannot stand the presence of a low pressure area and will rush to fill it, through every available void, thusly causing the rushing air to contact every surface of the heat exchanger.
Conversely if the fan was a pusher the rushing air would only contact the surfaces that constituted the shortest exit through them and not contacting them all.
This sounds good but seems the opposite of how our autos cooling systems are set up. But I can see where adding a shroud makes a low pressure area which increases efficiency. But our older Bolts didn't come with shrouds. So it seems in earlier autos the engrs depended on moving air from the vehicles forward motion to get enough airflow to make contact with all of the heat exchangers surfaces and that the fan was to be an aide when there wasn't enough air flow at idle and slow speed. In this case the fan being on the engine side didn't interfere with max air flow at speed. So how does this relate to the angle of the dangle? I dunno, just musing over a cup o joe.

Does anyone else think that we need to contact Mythbusters? I am sure that they could have some fun with this one!

Chris

Also, if you are using a fan shroud to increase electric fan efficiency, when one is moving fast, and the fan is off by the thermostat, opening the back of the shroud with a simple flap mechanism( look at VW small cars) allows more cooling air to pass through.

Ed

Pushing air through the radiator of an off-road vehicle like a tractor or a bulldozer has a very practical application that has nothing to do with thermal efficiency. It helps prevent the radiator fins from getting clogged by dirt, dust, or vegetable debris. When I'm bush hogging head-high vegetation in my pastures, the cloud of weed seeds and leaves getting blown out of the grill is a sight to behold. If you get your D-9 Cat going 50 MPH down the road and the airflow from the fan is opposing the ram air direction, all bets are off. Please mount a Go Pro camera so the rest of the world gets to watch your self-destruction, though!
Jerry

Well, on my outside A/C unit, the top fan blows up. If it didn't. I would have sticks, leaves, dirt and birds nests being sucked into the open space inside.

You bought a thicker radiator? New? used? Aluminum? Cleaned out? Why are you adding a fan for the 261? If a radiator does not cool, there is something wrong with the system. Do you have A/C?

The Electric fan industry is a little tricky with their info/ratings. The pusher is the same CFM as the puller. Don't let that fool you. Of course it is, it's just like taking a house fan and pointing it in one direction, then pointing it 180 deg in the other. We want to know the efficiency of the air flow AFTER mounted to a test radiator. There can not be the same efficiency for both. The pusher would seem to be fighting normal air flow from forward motion of the vehicle. It would seem that the plastic "frame" would block more forward motion air. It would seem that the puller would have more air to direct onto motor if spaced and/or shrouded. Another test we would want to know is how soon the thermostat shuts fan off on pusher and on puller under same conditions. Good luck finding that. They only have pushers for guys with no room for puller. A large eFan is necessary and a shroud, otherwise only some of the radiator is utilized.
Flex-A-Lite says a pusher is 80% as efficient and a puller. So there you go, can't go by same CFM.

The radiator I bought was thicker to handle adding A/C later. It was brand new. I test fit it before I took everything apart, and it makes everything a bit close. I will be putting things back together soon and will know if I can move the radiator forward enough. I plan to use the "proper" fan if possible, but I want to make sure it cools, whatever method I have to use. This is intended to be my daily driver.

Close is good. Non flex Fan with no shroud...3/4-1" clearance. Many say 1/2" is the ideal number. Be sure that when finalizing location you take in to account any tilt the motor/fan blade may have relative to radiator face. Hopefully they are parallel.

GMC trucks mount the radiator midway through the core support, you might move yours fwd like GMC's.

Ed

All sound advice. Can't wait to get to that point.