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Engine Fan question?

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Norton47

Jedi Warrior
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As I am tidying up the engine bay in preparation to install the rebuilt motor, I have been going back and forth on the question of which fan to use. The car came with an electric fan installed in a pusher configuration. It is the smaller size and seemed to do an adequate job, once I had installed an override switch for around town driving. I just didn't like it cycling all the time. With the override switch I could keep it at just above normal in stop and go traffic. Still had to watch out on the hottest days for fuel line vapor lock.
Anyway the car also came with a 13 blade red fan.
The main reason the PO installed the electric fan was the horsepower gain. This is minimal in my mind and I am going for stock anyway. I want the best cooling.

I am leaning towards installing the mechanical fan and removing the electric fan, what say the savvy ones?
 
Really depends if you you want your car to be more original. Electric fans in the puller configuration generally perform better than pushers, so if you do it again, I would reverse what you had.

I've got an electric fan on my rig with the same exact electrical setup that you have (on/off/auto). Interestingly enough I didn't install it for the power gains, although I'm sure it does give some benefit in that department, but rather for the sound. My OEM fan was SOOO loud. With my electric fan even pushing 2300 cfm, I can't tell if its running unless the engine is off or the bonnet is up. Nice and quiet, just like it should be.

I don't think reliability is an issue if you properly wire electrics up, so to me it comes down to what you want for the car.
 
the trouble with an engine fan is , besides noise etc.,when you need the fan the most your engine is usually at an idle which results in least air movement.The electric fan is at max output at the flip of a switch or in auto mode.

i'm running a pusher fan on mine wired like Shannon's and it works just fine.I'm using a 12" hayden which has been in there for about 12 years now with no problems yet.The other thing I like about electric is,when you park after a long run in hot country,the fan will cycle after shutdown.(wired to direct fused power)for faster cooling.
 
Ok, great condsiderations, but if I want to go to a puller fan configuration, I will need to make or buy a different harmonic balancer bolt and extension piece, correct?
The electric fan won't fit between the radiator and the fan extension piece will it? I would also need a shorter bolt then?
 
Norton47 said:
Anyway the car also came with a 13 blade red fan.
The main reason the PO installed the electric fan was the horsepower gain.
Click to expand...
Interesting theory ... did he think the electric fan was going to help pull the car through the air ?

The power gain, if any, comes from the engine not having to power a fan when no fan is needed (ie electric fan off and NO mechanical fan). Varies by car of course, but IMO it's usually too small to notice. We've all heard stories of the fan consuming 5-10 hp; but on most cars it's driven by a fan belt that is simply incapable of carrying that much power for very long; and also has to turn the water pump.

There might also be some improvement in fuel mileage (for the same reason), but it likewise won't be much.

And when the electric fan is running, it probably draws as much power from the engine as the mechanical fan did. Car alternators aren't all that efficient and neither is that fan motor.
 
The only big plus I can see with the use of an electric fan is in stop and go traffic, where with one you get maximum air flow even when stopped.

Also, the mechanical fan, which bolts to the front of the crankshaft, is really a propeller that pulls the crankshaft forward applying constant pressure on the thrust bearing. Not a big deal, but the electric would eliminate this condition.
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:] Also, the mechanical fan, which bolts to the front of the crankshaft, is really a propeller that pulls the crankshaft forward applying constant pressure on the thrust bearing. Not a big deal, but the electric would eliminate this condition.[/QUOTE]

Thanks Ray. I never really thought of it that way, but you are right.

I just may go to the electric when I switch blocks over next fall.
 
TR6oldtimer said:
...the mechanical fan, which bolts to the front of the crankshaft, is really a propeller that pulls the crankshaft forward applying constant pressure on the thrust bearing...
Click to expand...

Granted I have the 4-cyl flavor of Triumphs but I have a hard time imagining this effect.

I don't think I could move the crank forward by blowing on the fan blades (indeed it takes a good lever) so it is hard to expect the air moved by those blades getting enough push to move the crank.

Interesting thought though.
 
Great, then it's propelling me fwd too, thus offsetting the HP drain!!! We can only hope, interesting thought though, never heard that one before.
 
I guess a good test would be to rev the engine with a fan on it and hold a light on the damper to see if it moves forward. If not, no big deal.

If it does, then we need to find a car without a fan to see if it moves forward when revved up. If it does, removing the fan didn't matter.

If it does not, we have something to talk about.
 
Not an original thought on my part. From How to restore Triumph TR5/250 & TR6 pg 79, top right paragraph.
 
Brosky said:
I guess a good test would be to rev the engine with a fan on it and hold a light on the damper to see if it moves forward.
Click to expand...

If the usual movement is 0.010", I think you'd have a hard time seeing that on a running engine given the movement from vibration, etc.

I would be surprised if there was much thrust from the fan so I wouldn't expect this to be a big factor. To me that biggest deal is whether you have overheating in stop and go traffic. I know I had a lot of trouble with that this summer so I may add a fan when the car goes back together.

Bryan
 
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