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I am after some specs for a clutch fan and thought someone (Dr Terry) may know them.
I am using a 7 blade (Holden) air con fan with a thermatic clutch hub on my 355. I would like to understand how it works.
At what temperature does the fan start to drive and have full drive?
What speed does the fan turn at compared to the water pump speed?
How much air would this pull compared to say a spal 3000cfm electric fan ?
The reason I am asking these questions is because if this setup doesnt give me "full" fan until say 190F and I am trying to run my engine at 180F, then maybe this is the wrong fan setup.
My current clutch hub is a replacement unit (probably not genuine Holden) - do you know what is the correct replacement (maybe a davies craig product) ?
Thanks in advance - Ray.
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Hi Ray.
Im somehow missed this query the other day, but I will try to answer anyway.
Firstly, I doubt you will find any real specs for viscous fan clutches, but I can tell you from experience they will easily out-perform any single electric fan on the market. Late model dual-fan setups (e.g. VT-VZ & AU-BF) are quite good but they are the only electric fans that will equal the performance of a GM 7-blade with a viscous clutch.
They must be used in conjunction with a factory type shroud or they just dont work effectively. The way they work is relative simple. They have a small bi-metallic temperature-sensing coil on their front face which senses the temp. of the air coming thru the radiator. As the air approaches the 90-95 degree (C) region, the vanes inside the clutch begin to couple up. By 100 degrees (C) the fan should be driving a 100% water pump speed, which will have so much airflow that you can hear the roar. If yours isnt working like that, fit a new clutch. There are various brands on the market, Im not sure if genuine GM is still available but I use Dayco & they are just as good.
Dr Terry
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There are only 3 types of people in the world.
1. Those who make things happen.
2. Those who watch things happen.
3. Those who wonder what happened. |
If at first you don't succeed, just call it Version 1.0 |
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Rank: Member
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Joined: 24/11/2009(UTC)
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Thanks for the reply - I can now see that I may be expecting too much.
I have a 430hp 355 with large cam and 3500 stall (all the stuff that adds to heat) in a HQ ute. PWR Alum cross flow. My fan shroud is a home made one adapted to suit the 7 blade and PWR radiator and is a aluminium straight sided shroud that is about 20mm bigger diam. than the fan and has half the fan in and half sticking out - this means about 75% of the core is covered.
I like to run the engine at 180 max - I know this is a little low but I have a stubbon idea in my head that once it starts to get too hot it will be that much harder to cool it down - so I guess I am trying to have some safety margin.
If I am not getting lots of fan drive until around 95c (203F) then maybe I am asking too much.
Maybe I need to go back to a normal HQ design radiator so I can use the proper shroud that covers the whole core. This would have to increase the efficiency of the fan even though it wont be driving at 100%.
Another idea I had was to fit a 12" pusher electric fan onto the front of the radiator just for those times when I really need it. Do you think this will help.
I am not a Radiator engineer, but the PWR radiator is very thick, you can hardly see through it - they say this is the normnal type they supply to anyone with my type of "performance".
Thanks for your reply - your knowledge is much appreciated.
From what I have written above, can you comment and have you any suggestions that may help.
Once again - Thanks - Regards Ray.
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Im in the process of fitting a chev V8 radiator to my HQ. It came out of an HQ with a big block. Along with the radiator came a nice shroud. Now i dont think this will work with a 202s stock steel fan.
Ive been told to get a blue motor water pump (bigger bearing) and clutch fan. Is this accurate? And if so, what actual fan am i looking for? |
"Silly modern cars" |
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I currently have the viscous fan on my HZ with the shroud. I have a cold thermostat in it as well.
It also has A/C, but i have hooked up the electric fan via brake light switch and through the pollution switch on the back of the head.It will also work full time when a/c on.
What happens with mine is when the head temperature gets up over say 60 degrees, i put the brake on and the electric fan comes on.
If the a/c is on electric fan goes all the time.
On most days over 35 degrees the temp gauge never goes over 1/2 with a/c on, except if in Sydney traffic where itll get up to just under 3/4 but never higher.
On a normal day temp gauge wont go over 1/4 for all the above reasons.
Hope this will help
HJ Sandman Pano, HZ BO6 Pano
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