Electric Fan Questions:

How big of a fan will fit in a stock radiator sized application. I see 14", 16" etc...

So theres a lot of room for contreversy concerning electric/engine fans, but what about an electric water pump? When I see them in summit, jegs, etc, they say "for drag use only" or something like that. what would be the advantages?

I wanted to address 2 things.

By design.. a pusher or puller fan will move the same amount of air and will have exact same efficiency's.

Think about this guys... every fan is a pusher AND a puller. Only difference is what side of the fan the motor and shroud is on and thus what side of the radiator the fan is mounted on.

So why do most automotive manufacturers use a puller fan? Well 1st off, not all do. But the main reason is because if it's in the engine compartment, the fan is more protected. Both from weather, but also from debris.

2nd. Engine temperature is controlled by your thermostat. NOT your fan or radiator. The only time your engine temp will fluctuate with an electric fan is if your cooling system is inadequate and the temperature inside the radiator starts to climb above the temperature in which your thermostat is designed to open. However, by this time the electric fan will be on non-stop and thus it really won't make a difference if your running an electric vs. mechanical fan.

70_Nitrous_Eater said:

I wanted to address 2 things.

By design.. a pusher or puller fan will move the same amount of air and will have exact same efficiency's.

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Sort of. If the car is moving forward a puller is more efficient, because it's assisting, rather than pushing against the airflow coming in through the grill. Although this would be tougher to measure, I'd hazard to guess it is more efficient even if the car were moving backward. The air in the engine compartment in most likely hotter than the air surrounding the car. So, a puller would be drawing in cooler air. Cooler air equals more heat transfer which is what you want.

70_Nitrous_Eater said:

Think about this guys... every fan is a pusher AND a puller. Only difference is what side of the fan the motor and shroud is on and thus what side of the radiator the fan is mounted on.

So why do most automotive manufacturers use a puller fan? Well 1st off, not all do. But the main reason is because if it's in the engine compartment, the fan is more protected. Both from weather, but also from debris.

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Protected from what? If the fan is pushing debris from the engine compartment into the radiator, I'd be the first to ask why. If so, a fan shroud could help here and also increase efficiency by helping to direct the air flow.

70_Nitrous_Eater said:

2nd. Engine temperature is controlled by your thermostat. NOT your fan or radiator. The only time your engine temp will fluctuate with an electric fan is if your cooling system is inadequate and the temperature inside the radiator starts to climb above the temperature in which your thermostat is designed to open. If this occurs, then your cooling system is inadequate.

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All things being equal, yes. A manufacturer designs an engine to run at thermostat temperature. I've heard discussion on this site the reason a car overheats is the coolant doesn't stay in the radiator long enough to cool. It's a strange way of making the argument of inadequate heat transfer. An electric fan doesn't make up for an inadequate cooling system, but it helps to transfer heat. I've never heard the dual Spal fans on my '67 come on while I'm in motion, but certainly at idle.

Don't forget if you ever find yourself running hot for whatever reason, turn on the heater (extra heat transfer) as a temporary measure.

Steve C.

70XR7ConvertCat said:

Sort of. If the car is moving forward a puller is more efficient, because it's assisting, rather than pushing against the airflow coming in through the grill. Although this would be tougher to measure, I'd hazard to guess it is more efficient even if the car were moving backward. The air in the engine compartment in most likely hotter than the air surrounding the car. So, a puller would be drawing in cooler air. Cooler air equals more heat transfer which is what you want.

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Hold on here... doesn't matter if you have a pusher or puller fan. Air flow is always in the same direction. Trying to reverse the airflow is a really bad idea for the exact reason you mentioned. I think your getting confused here. Pusher or puller means wether the fan is designed to push or pull the air through the radiator. It has nothing to do with the actual direction of airflow.

Protected from what? If the fan is pushing debris from the engine compartment into the radiator, I'd be the first to ask why. If so, a fan shroud could help here and also increase efficiency by helping to direct the air flow.

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Again.. the direction of airflow is the same. Puller fans are always inside the engine compartment. Thus they are protected from alot of moisture, salt, sand, etc..

All things being equal, yes. A manufacturer designs an engine to run at thermostat temperature. I've heard discussion on this site the reason a car overheats is the coolant doesn't stay in the radiator long enough to cool. It's a strange way of making the argument of inadequate heat transfer. An electric fan doesn't make up for an inadequate cooling system, but it helps to transfer heat. I've never heard the dual Spal fans on my '67 come on while I'm in motion, but certainly at idle.

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A fan is part of a cooling system. And more airflow (as a result of moving to a high flow electric fan for example) will definately improve cooling. The arguement about the amount of time the coolent spends in the radiator is completely wrong and I really hope you don't believe it. I can go into detail on why if you want.

You are correct.. in a properly designed cooling system, the fan is not needed while the car is moving (15+ MPH). This is the theory behing "flex fans" they actually flex in relation to engine RPM and not speed, but it's a fairly safe bet that if your engine is above 2500rpm for more than a few seconds that your car is probably in motion and not staying still. Even then, the flex fan still moves air..just not as much as a traditional fan would. Same thing goes for fans with clutches.

Don't forget if you ever find yourself running hot for whatever reason, turn on the heater (extra heat transfer) as a temporary measure.

Steve C.

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Finally something we agree on. Personally I've found that it doesn't make much of a difference, but it will buy you some time if your stuck in traffic or something.

As a side note to this. An external oil cooler with fan will also have the same effect.

70_Nitrous_Eater said:

Hold on here... doesn't matter if you have a pusher or puller fan. Air flow is always in the same direction. Trying to reverse the airflow is a really bad idea for the exact reason you mentioned. I think your getting confused here. Pusher or puller means wether the fan is designed to push or pull the air through the radiator. It has nothing to do with the actual direction of airflow.

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The direction of airflow is the same, or it should be. Having said that, it was quite common for mechanical pusher fans (particularly on older cars) to be in the engine compartment. Sort of defeats the purpose. Later came clutch, and flex fans, so not as much of a big deal.

Electric pusher (outside the engine compartment), and electric puller fans (inside the engine compartment) are common in contemporary machines.

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70_Nitrous_Eater said:

A fan is part of a cooling system. And more airflow (as a result of moving to a high flow electric fan for example) will definately improve cooling. The arguement about the amount of time the coolent spends in the radiator is completely wrong and I really hope you don't believe it. I can go into detail on why if you want.

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No, I don't believe it and that was my point. The entire issue is one of heat transfer. More surface area will equal more heat transfer. You get more surface area by using additional rows, or a larger radiator. Thermodynamics lesson for the day.

I'm all for the electric fan setup, I did my conversion with a big fan with shroud that I pulled out of the Junk Yard for 15 bucks. I've got the low speed running all of the time (key on) and the High speed kicks on at 185 via a temp switch. Works great. And those whinjin about all of the amp draw, I've done the GM 12si (94amp) alternator conversion with no prob, works great and quiet too!!!

Here's a pics of the Fan and alternator mod





Fan and Alternator Mod

and the fan wiring

http://www.ghettonet.org/images/mustang/2speedfan.jpg

My £0.02:

Electric fans are better than mechanical because:

1) They only come on when you need them, reducing load on the engine.
2) The give more room in the engine compartment for engine (if you have a pusher).
3) Mechanical fans are noisy, you blip the throttle and it sounds like a Huey flew over (particularly with sixties technology).

Pullers are more efficient because they draw the air through the radiator, and will flow as much as they can pull; trying to push air through the rad will cause the airflow to stall because the fan is able to 'grab' loads of air, but can't discharge it all.

Straight blades are more efficient, curved are quieter (someone already said this).

If you can, get a fan with an odd number of blades, that are not equally spaced (they do something clever to keep 'em balanced), because you're less likely to get harmonics which can give vibration or some awful noise under some conditions.

If you regularly get stuck in traffic in the dmiddle of Death Valley (like that ever happens) then you might want an engine fan, a puller and a pusher...

Besides an electric pusher fan lazily idling behind the grille looks cool.

I've got one of those fans with the odd # of blades if one of ya hard core guys wants it

well, Ive done quite a few diff fan setups, diff waterpumps and came up with one that works well.

1) those permacool elect fans with the metal blades sux. They work actually better as a pusher than a puller.

2) Derale or however you spell it, ROX. Best fan Ive owned.

3) I run the 50gpm Electric water pump and it works awesome. Always on when the car runs. I will prob cycle the fan with temp, not the waterpump. Reason being, if you dont move water thru the engine at all times, you will get hot spots in your heads and can cause detonation issues. Not worth it to me, and now Ive had this elec WP for about a yr, no probs at all. Actually seems to cool as good or better than my Edelbrock WP I had prior.

This coming from the 6-71 engine with pretty high cooling demands, on a mild NA engine I dont think anyone would ever have an issue with a decent radiator.


I should add, some fans work better as pushers than pullers. Acutally most always do better as a puller. That permacool was an acception. Performed a ton better as a pusher.


As for the water pump comment, I deal with water pumps for a living every day. Just cause you can spin that pump by hand and feels like no load, at 3000-6000 rpm moving 60gpm or so is a totally different story. Ill give you a 60hp Irrigation pump and sure, you can spin it by hand with no issue, but the moment you start moving 60gpm at 3450 rpm good freakin luck.

I brought this thread back from the dead with a simple question guys.... What size electric fan will fit a stock sized radiator on my 67, 289 car? You guys are great in debating all this technical stuff.... how about the simple stuff?

CornerCarvin67 said:

I brought this thread back from the dead with a simple question guys.... What size electric fan will fit a stock sized radiator on my 67, 289 car? You guys are great in debating all this technical stuff.... how about the simple stuff?

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The best thing to do is just measure your radiator and find a fan that fits the best. I am going with a single 16in fan. I dont have my info at work so I cant give you part #'s right now.

CornerCarvin67 said:

I brought this thread back from the dead with a simple question guys.... What size electric fan will fit a stock sized radiator on my 67, 289 car? You guys are great in debating all this technical stuff.... how about the simple stuff?

Click to expand...

If your radiator is stock, it is probably 20". Perhaps 24" if someone pirated a big block rad along the way. First decide whether you want to run a fan shroud or not. It seem to me a 16"-18" fan is what you're looking for.

Thanks guys... I guess I'll just run with the 16" straight blade puller from streetortrack.

Dual Fans

My 67 with 351C always ran warm until I put in a Howe alum radiator and dual 12" pull fans. Made a huge difference. Only issue was that a Cleveland has a dry intake manifold so there was only the block sending unit location for a thermo switch. I decided to run mine hot with a switch in the cockpit and 30 amp relay.

On my Cleveland I used a water outlet from a 351m motor as it has two sender ports in it.I am using one for my fan.I think the one thing that is missing in the pusher-puller debate is the fact that most fans use a shroud that is wider at the rad side and smaller at the fan.If you mount the fan in front of the rad the shroud is going to block natural airflow, kind of like trying to pour something into an upside down funnel.The fan I am using I pirated from an Audi at the wreckers, It is a dual 11" fan with one fan motor driven and the other belt driven off the first.The shroud is steel which made it easy to weld up brackets attaching it to the top of the rad and the bottom fits nicely into the stock shroud brackets.It also only needs about 12 amps to run it so I haven't had to upgrade my electrical system.