52 replies to this topic

[Ando]

As the title suggest.. I can't believe the rhetoric I'm hearing about me deciding to use a mechanical fan over a thermos! I do know the pros & cons with both but losing a couple horsepower with a mechanical doesn't bother me. Stories of fan blades flying off, going through bonnets & maiming people..well I've heard that one more than once!

Mechanical fans have been around for a hundred years but now none are any good! lol Don't get me wrong, Thermos are a good thing but what's so wrong wanting to use a traditional engine fan!

 

 

 

[BIG KEV]

The main reason I will be going thermo's is when sitting in traffic on a warm day your motor is only at very low revs and Thermo's are either on or off meaning the car can be at stand still and there is still air flow through the Radiator when the fans are on

[S pack]

I have both.

[Cook]

I guess another factor is space and or running gear.  I'm looking at a serpentine system which will run with thermo fans.  Cheers Ron

[N/A-PWR]

Great thread Ando,

 

I am a mechanical fan fan,

 

where it is simplicity, cheap and reliable,

 

and as for stranded in traffic, an extra radiator core was sufficient. 

 

mind you, I was using the holden 6 flexi an no shroud:-

 

http://www.redlineau...px#.VsLdaLR97Mo

 

did however develop cracks from 7500rpm continuously over several motor changes. 

[rodomo]

7hp on an SLR 5000 according to some stuff I have here from a Modern Motor test. Lack of constant noise would be the biggest benefit IMHO.

Edited by rodomo, 16 February 2016 - 08:55 PM.

[gtrboyy]

Only real reasons to go thermofan is cosmetic or simply lack of space.Au fans or single bf fan with 110amp alternator work great

 

Mechanical fan espoecially clutch type things in early commodores with proper shroud damn near unbeatable..sure they're noisey & take up space but really are 1 less headache to worry about when done right.

 

Lots of street driving I'd prefer mechanical fans if more drag racing maybe thermofans with a switch so can cool car down between runs or just turn off to race.

[I'm a Red Motor fiend]

Ando, good choice mate. The only reason I dont run one is due to the Romac balancer.

Ando, good choice mate. The only reason I dont run one is due to the Romac balancer.

[warrenm]

Until I fitted an ATI Super Damper to my 202, I ran a std Holden fan. Never made any difference to times down the 1/4.

[Ando]

Thanks for the input guys..

I got snookered when I ordered my radiator from PWR! I was talked into using their large tank (88mm) because I'm running AC, PS & the motor is grout filled up to the welsh plugs. Yes it will be a stout streeter (95%) club circuit (5%) use.

They convinced me that any 500+ hp motor with AC & PS will need their large radiator. I did say to them I also low mounted my AC compressor & integrated the PS to the left side.

When I received my radiator, I noticed PWR welded the 100mm C channel flush to the top & bottom tanks on engine side, leaving a 12mm gap on the radiator support panel side. mmm!! Too late now, the radiator is powder coated black.

Between the low mounted AC compressor & the 100mm lost from the radiator, space was getting very tight! If I had that extra 12mm lost by the radiator, I could have just enough for a slim thermo set up!

Anyway, I thought I'll run a fan & see how the cooling goes & if I really need an auxiliary thermo, I can run a 12" pusher on the drivers side for those hot days or track cool down times.

I'll see how it all goes but I reckon it shoud be OK though!

 

Cheers

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[ozyozyozy]

The best is a mechanical for pumping air through a radiator.
The vn v8 fan with viscous hub can keep just about anything cool.
Electric fans, as stated require bigger alternator, if you do the sums, need close to the 110amp for most people(thats using 2 thermos) problem that, MOST of the 110 alternators are not rated for more than about 5500- 6000rpm.
Electric can make them rev a little freeier, unloads the eng more but most will struggle in the really hot days to cool the engine mainly keeps them stable due to they just cant pull as much air as a mechanical fan.
Room is usually the biggest deciding factor in fitting one or the other.
Thats my 2 cents😊.

[UCgazman]

The best is a mechanical for pumping air through a radiator.
The vn v8 fan with viscous hub can keep just about anything cool.

 

Yep^ that what I run...

[76lxhatch]

Those riveted flexi fans do have a bad reputation for blades coming loose and out of balance, not sure if this is due to cheap and nasty versions or just in general. That will be why people are making those comments. Yours appears to have a pretty big hub which spreads the rivets a good way down the blades compared to some.

 

The clutch fans also have their issues when old or if they have suffered some small amount of damage - sudden acceleration can sometimes be enough to fold up blades when hot and the clutch is engaged.

[StephenSLR]

Stories of fan blades flying off, going through bonnets & maiming people..well I've heard that one more than once!

 

Never heard that one; not using an original fan anway, if you're going to go mech, avoid cheap flimsy Chinese fans.

How are you going to use your car? If you need the room or want to shave a poofteenth from your quarter time then go thermo otherwise mech. should be good enough; an overflow bottle is a must imo.

 

s

[N/A-PWR]

Factory metal blades can break too Steve:-

 

http://www.gmh-toran...ng/#entry895682

 

Lucky no-one was around. 

 

Never heard that one; 

 

s

[StephenSLR]

Factory metal blades can break too Steve:-

 

Wow; haven't heard it happen to a Torana. That's not to say it can't happen but it wouldn't be my argument against putting in a mechanical fan.

I have a 16" Davies Craig behind a 3-core; I guess I was a bit ambitious with my engine plans back in the day; ended up just putting in a mildly worked 308. I still have the clutch fan and if the thermo gives me problems it's going back on.

 

s

[orangeLJ]

I ran a spaced mechanical fan to clear the romac balancer..

The fan and the radiator are now hanging on the shed wall after starting an intimate relationship when the clutch was kicked into a corner at around 5000rpm

[EunUCh]

Agree with the viscous type if room allows,funny how things like this happen.

Dropped in to a friends place who tampers with engines from time to time,and even though the over heating fault was on 

a tojo it so happened that someone else who had the same model but turbo was there and it allowed us to check out how they work.

 

Most people spin the "clutch' type when the engine is off and feel some drag and then the thing frees up a bit and think the fan is

stuffed,this is not so,they have a bimetallic spring that controls 2 "reed" type valves that open ports when the spring warms up that

allow the fluid to travel into what is basically a small dyno. which "locks" the fan on and off depending on temp.After checking what happens when the engine was up to temp on the tojo with heat problems we then did the same thing on the turbo model.

 

On the one with the stuffed clutch the fan was "stiff" to turn and it nearly cooked itself.

On the turbo thing the fan was a bit draggy at first when turned by hand then freed up,we fired up the turbo job and got it hot and played around for a bit and we could actually see/hear the fan change phase and feel the heat  the thing was pumping when needed,they actually follow what the radiator is doing and sort of  "hunt" ever so slightly to try and keep the thing ok.

 

We ended up dismantling the stuffed one completely,what a piece of work they are.

Some will say the clutch type sap more power than conventional but as usual that is probably a debatable topic all on it's own.

 

Or, as most people use AU thermos,they will keep a fairly warm 351 cool....just something about some of the OEM stuff that works to some extent even if fitted to other breeds?.

I would be careful about some of the CFM numbers on the after market stuff.

[toryman76]

I am glad I found this topic. When I first started nutting out my engine build I was originally set on fitting AU thermo's. I know they are reasonably easy to fit but for me (and my engine a mild 304) I wanted something simple and more original looking. I've now decided that the clutch fan with shroud is the way to go and its interesting reading that this type of setup is potentially more effective at cooling than thermo fans. Does anyone have any photos of a square blade clutch fan fitted with a H-series 3 core radiator and the H-series shroud in an LH-LX? I have found some in this thread here but keen to see as many as I can find.

[jd lj]

Does the AU falcon thermo fit on a LC/LJ or only on LH/LX torana's?

Does it fit on the engine side or the grille side of the radiator?

I'm interested in fitting a thermo fan to my LJ but want one to go in front of the radiator so I can keep the engine bay looking more like the factory set up. The only time I really need it is if I happen to get caught in a bit of traffic in summer. It'll be good piece of mind though for the rest of the time, also handy when synchronising carbs or setting 6 idle mixture screws and the engine is idling for any decent length of time.

What other types of fans are LC /LJ guys using?

I'm also wondering about if I should use a simple on /off switch or an automatic temperature operated switch. Where does the sensor go on the auto switches, can I fit it to the bottom of the radiator out of sight?

Any pictures would be great.

[StephenSLR]

I'm interested in fitting a thermo fan to my LJ but want one to go in front of the radiator

 

If you fit them in front of the radiator you flip the fans over in the shroud so they push air into the radiator and you also reverse the polarity so they spin the other way.

 

s