Fan Clutch
Thread Starter
Instructor
Joined: May 2006
Posts: 118
Likes: 0
From: Sydney NSW
Fan Clutch
My 80 vet struggles with the Aussie summer and regularly overheats. I was considering a fan clutch system as I have been told they move a lot more air than thermos.
I don't quite understand how the clutch units works. If the fan doesn't spin faster than the motor, how does this help at standstill with high temparatures?
I don't quite understand how the clutch units works. If the fan doesn't spin faster than the motor, how does this help at standstill with high temparatures?
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
Your car came equipped with a clutch fan from the factory. Whether it is working or not is another story. Rather than trying to re-engineer the system or take wild guesses at what's wrong, why not diagnose properly.
How do know it's actually overheating?
How do know it's actually overheating?
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,847
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
With Mike! The clutch fan works differently than a flex fan. A flex fan will turn with the engine even at high RPM’s on highway driving this will restrict the air flow through the radiator.
With a clutch fan design, it will disengage on the highway and allow more air to pass through the radiator.
Also, most original fan blades are larger, have more pitch and sit closer to the radiator than the flex fans which will draw more air at lower PRM’s.
If the car is stock, go with the original set up. Make sure you have the correct fan shroud too! It shoud have the part number molded in the shroud.
I’m curious too, what are the symptoms of the overheating? Have you checked the timing? Have you checked the temperature with an IR gun?
Willcox Inc.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,847
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
I've used this part and never had a problem with it either.
The issue for this customer is the clutch can not be shipped oversea's. (the oil inside).
He will have to try to find one down under, or find someone here willing to take a risk shipping it.
Willcox
The issue for this customer is the clutch can not be shipped oversea's. (the oil inside).
He will have to try to find one down under, or find someone here willing to take a risk shipping it.
Willcox
Drifting
Joined: Jul 2002
Posts: 1,944
Likes: 20
From: The only Corvettes in Highett Victoria
Go electric
patto,
G'day mate, welcome to the Forum. Willcox gives good advice, but don't waste your money on dinosaur technology. Get yourself a proper single or dual electric fan set-up and use a full fan shroud that forces all of the air through it. Power the fan(s) from a relay that gets its power straight off the alternator through a 10 gauge wire and signal the relay with a switch mounted at either end of the top radiator hose, or thereabouts.
I made a custom fibreglass fan shroud and use a single 16" fan on my '74 coupe. It gets power through a relay and the signal comes from a thermal switch that is mounted between the fins just under the top radiator hose inlet. Works fine.
An added advantage is that the fan is parallel with the radiator and blows the hot air down to the road rather than straight back over the top of the engine.
Contact me if you wish at jc.smith@optusnet.com.au .
Regards from Down Under
aussiejohn
7 months to go
G'day mate, welcome to the Forum. Willcox gives good advice, but don't waste your money on dinosaur technology. Get yourself a proper single or dual electric fan set-up and use a full fan shroud that forces all of the air through it. Power the fan(s) from a relay that gets its power straight off the alternator through a 10 gauge wire and signal the relay with a switch mounted at either end of the top radiator hose, or thereabouts.
I made a custom fibreglass fan shroud and use a single 16" fan on my '74 coupe. It gets power through a relay and the signal comes from a thermal switch that is mounted between the fins just under the top radiator hose inlet. Works fine.
An added advantage is that the fan is parallel with the radiator and blows the hot air down to the road rather than straight back over the top of the engine.
Contact me if you wish at jc.smith@optusnet.com.au .
Regards from Down Under
aussiejohn
7 months to go
Race Director
Joined: May 2006
Posts: 16,528
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From: Dayton, Ohio
Oil -thats interesting-did not know that.
Le Mans Master
Joined: Apr 2004
Posts: 7,106
Likes: 38
From: Newark DE
you may consider fan clutches "dinosaur technology" but they DO work and work well and are very reliable, have a low failure rate, and are inexpensive, especially compared to an electric fan set-up. Why re-invent the wheel when you don't need to?
BTW, many might consider the basic Chevy small-block push rod design motor "dinosaur technology" also but guess what, it's still the basic design behind the incredible new LS9 motor which is an engineering masterpiece.
If you prefer electric fans because you may want to "clean-up" the look of the engine bay by removing a fan and shroud, or wish to add one for some other reason than that's one thing, but don't discount the usefulness of a basic fan/fanclutch set-up just because it's design and use dates back a number of years. The reason it was used for so long was because it worked.
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Thread Starter
Instructor
Joined: May 2006
Posts: 118
Likes: 0
From: Sydney NSW
Yes thanks for all of this, I gather you can't keep the mechanical fan as well as the thermos?
I am leanin toward the clutch fan particularly as I had a thermo which shorted and left me stranded.
As for the heating the motor cruises around the 180 degree mark moving quickly into the 230 degree mark if caught up for 4 5 minutes or so at standstill on a hot day.
It is interesting you mention timing, I have just had a crate motor (A C Delco) installed and the heads had to be modified after 15 months (say 1000kms, 650miles) due to incorrect seals.
We have done an arbitrary timing and carby adjustment since and the car does seem to run hotter at standstill and the vacuum seems to have varied to the extent the brake pedal seems to also travel further. Can all this be related?
I am leanin toward the clutch fan particularly as I had a thermo which shorted and left me stranded.
As for the heating the motor cruises around the 180 degree mark moving quickly into the 230 degree mark if caught up for 4 5 minutes or so at standstill on a hot day.
It is interesting you mention timing, I have just had a crate motor (A C Delco) installed and the heads had to be modified after 15 months (say 1000kms, 650miles) due to incorrect seals.
We have done an arbitrary timing and carby adjustment since and the car does seem to run hotter at standstill and the vacuum seems to have varied to the extent the brake pedal seems to also travel further. Can all this be related?
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,847
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
The oil in the clutch fan restricts the ability to ship. (Unless you just want to wing it and take a chance). It would be my luck the plane would crash and we would get blamed for it. It’s kind of like the 3M weatherstrip glue, dye and any other liquid that has a lower flash point.
I shipped a crate motor (The old GM target master engine) to Germany about 20 years ago and the customer wanted GM oil and GM anti-freeze.
We could ship the engine but the oil and anti-freeze could not be shipped either by UPS or by direct flight! The air line wanted to know the flash point of anti-freeze or ethylene glycol. I didn’t have a clue what the flash point was and at the time did not persue how to find out. I shipped the engine but nothing else.
I was shocked but yes there is a flash point for ethylene glycol. Must be hotter than hell is all I could think of. Unless they have relaxed this in the past twenty years I would not think you could ship one overseas.
Willcox Inc.
I shipped a crate motor (The old GM target master engine) to Germany about 20 years ago and the customer wanted GM oil and GM anti-freeze.
We could ship the engine but the oil and anti-freeze could not be shipped either by UPS or by direct flight! The air line wanted to know the flash point of anti-freeze or ethylene glycol. I didn’t have a clue what the flash point was and at the time did not persue how to find out. I shipped the engine but nothing else.
I was shocked but yes there is a flash point for ethylene glycol. Must be hotter than hell is all I could think of. Unless they have relaxed this in the past twenty years I would not think you could ship one overseas.
Willcox Inc.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,847
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Ouch, Now that's cold! 80's technology being dinosaur. That really makes me feel old! 
The original set up should be able to cool your car just fine! However, the electric fans would probably me more accessible to you down under. Dinosaur technology from a car built in the 80’s? Dinosaur technology is from the 50’s to me!
Now I’ll have to go take some Geratall and go to bed. 
Willcox
The original set up should be able to cool your car just fine! However, the electric fans would probably me more accessible to you down under. Dinosaur technology from a car built in the 80’s? Dinosaur technology is from the 50’s to me!
Now I’ll have to go take some Geratall and go to bed. Willcox
Le Mans Master
Joined: Apr 2004
Posts: 7,106
Likes: 38
From: Newark DE
Correct timing and correct vacuum advance set-up is very important and can make a significant difference to the operating temp of the motor.
Make sure your total timing is at 36º (with the vacuum advance hose disconnected and plugged). Than see where your initial timing is falling with the total timing set up to 36º.
Next, reconnect the vacuum advance cannister and make sure it connected to a full manifold vacuum source, not a ported one.
Oh, if you made any changes to the motor from stock, such as a cam change, you may need to change out the vacuum advance can to a more appropiate one since modifications to the motor can cause a change in the level of vacuum the motor makes and if you aren't getting the correct amount of vacuum advance at idle it can cause higher motor temps
Pro
Joined: Jun 2008
Posts: 673
Likes: 2
From: Melbourne Victoria
Hi patto,
I got a replacement fan clutch from Davies Graig, good price too.
Haven't had a prob in 5 years.
I know they sell them from their outlets but I've seen them a Super
Cheap Auto too, here in Australia.
If you need any part Numbers, I can check the clutch when I get home from work tomorrow night.
Cheers
Gav
I got a replacement fan clutch from Davies Graig, good price too.
Haven't had a prob in 5 years.
I know they sell them from their outlets but I've seen them a Super
Cheap Auto too, here in Australia.
If you need any part Numbers, I can check the clutch when I get home from work tomorrow night.
Cheers
Gav
Thread Starter
Instructor
Joined: May 2006
Posts: 118
Likes: 0
From: Sydney NSW
thegavel,
I can source a clutch OK thanks but would appreciate the part no anyway to check.
What fan are you running?
The 8 blade corvette model is hard to source and it has been suggested to 4 blade holden model would be OK.
Appears people are divided on electric versus mechanical?
I can source a clutch OK thanks but would appreciate the part no anyway to check.
What fan are you running?
The 8 blade corvette model is hard to source and it has been suggested to 4 blade holden model would be OK.
Appears people are divided on electric versus mechanical?
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Both have their place depending on application.If you buy quality both are very good.I prefer the 7 blade fan and GM#88961768 clutch (no less and only GM).This combination CFM wise is very hard to beat.I doubt seriously that any electric fan setup can match it.(7 blade 17" fan with 250hp plus)With normal inspections a quality clutch fan will never let you down in an instant.
Pro
Joined: Jun 2008
Posts: 673
Likes: 2
From: Melbourne Victoria
thegavel,
I can source a clutch OK thanks but would appreciate the part no anyway to check.
What fan are you running?
The 8 blade corvette model is hard to source and it has been suggested to 4 blade holden model would be OK.
Appears people are divided on electric versus mechanical?
I can source a clutch OK thanks but would appreciate the part no anyway to check.
What fan are you running?
The 8 blade corvette model is hard to source and it has been suggested to 4 blade holden model would be OK.
Appears people are divided on electric versus mechanical?
Just had a look at my setup- 7 blade fan(Original)
and the clutch part No. is 2705 (there is a Heavy Duty
one P/No 2747).
Up until I installed my reco radiator last year
(I also put on a front spoiler)mine used to sit between 200 ^ 220 in summer, with the new rad it's never hit 200 (sits @ 190 in traffic & never higher than 180 when cruzin').
Where in Oz are you located ???
Hope this helps.
CHHERS
Gavin
Drifting
Joined: Jul 2002
Posts: 1,944
Likes: 20
From: The only Corvettes in Highett Victoria
Dinosaur technology explained
Barry K and Willcox,
I didn't mean to offend anyone, but facts are facts. No modern car that I know of comes with a belt driven fan and no electric fan. As for the 80's not being old, remember that the fan and shroud found on a 1980 model hadn't changed much since the first C3 came out in September 1967 - that's over 41 years ago - and in modern automotive terms, that's a dinosaur.
I did not say that the old belt driven fan wasn't good or didn't work well. I accept that they were designed with the technology of the time and they worked well. It's just that a properly designed and fitted modern electric fan/shroud system will work better. It will also free up a few horsepower and help the engine give better fuel economy, factors that are quite important these days.
Regards from Down Under
aussiejohn
7 months to go
I didn't mean to offend anyone, but facts are facts. No modern car that I know of comes with a belt driven fan and no electric fan. As for the 80's not being old, remember that the fan and shroud found on a 1980 model hadn't changed much since the first C3 came out in September 1967 - that's over 41 years ago - and in modern automotive terms, that's a dinosaur.
I did not say that the old belt driven fan wasn't good or didn't work well. I accept that they were designed with the technology of the time and they worked well. It's just that a properly designed and fitted modern electric fan/shroud system will work better. It will also free up a few horsepower and help the engine give better fuel economy, factors that are quite important these days.
Regards from Down Under
aussiejohn
7 months to go
Burning Brakes
Joined: Dec 2007
Posts: 952
Likes: 0
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 27
From: Florida
Big difference there alone.
For general info:
Heavy duty applications still come with the dinosaur stuff, like SUV, pickups and up, especially when towing is involved. Electrics not recommended for towing at all.
Makes you wonder a little, how dependable the latest tech really is.