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NCC Forum Home Page -> NCC - General Discussion -> How much more cooling is added when changing fan pitch from 27 degrees to 34.5 degrees?
Post Info TOPIC: How much more cooling is added when changing fan pitch from 27 degrees to 34.5 degrees?
jim larson


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How much more cooling is added when changing fan pitch from 27 degrees to 34.5 degrees?
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Since I added AC last fall I am thinking that the 34.5 pitch fan will more a lot more air than the 27 degree blade.  How much might just be a guess.  I noticed the corvette fans available seem to indicate the the 34.4 pitch was used on AC cars.  Maybe some of the other GM A body cars used a higher pitch on their ac cars, anyone know?  Maybe some 67 or 68 camaro's  or Impala's from 64-68 ; but I am not sure of the diameter of those blade.   Well I have to think about something with all this snow and cold.   Thanks



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Jim L

Lake City
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I ordered a heavy duty fan clutch for my car, should slip less when ingauged.

I don't recall, do you have a clutch fan or direct drive fan. If you have a clutch I would think you would not get the full benefit of the greater pitch fan as there would be more slippage with the clutch is ingauged. The heavy duty should keep the fan speed up much closer to water pump pulley speed, however you would need the larger center as there is no HD clutch available for earlier small fan centers. The mounting hub is universal.

 



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Bob W.

Lino Lakes
jim larson


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I have the small circle clutch that was used i n 66 and made by Eaton.  From my research I believe only a 5 blade fan, 18",  with a 26 degree pitch, and 5 rivets,  made by either Schwitier or Hayes-Albine was used in 66.  However it looks like in 65 there was a fan with a larger pitch 34.5 degrees used  on corvette or chevy BBC, But with a smaller diameter 17".

Then in 67 this went to having only 4 rivets. Then in 68 some cars got the small circle fan and some a newer big circle fan and 7 blades.

I am thinking that having the correct clutch with the correct mounting distance that sets the fan into the shroud correctly  might have more of an impact then an aftermarket heavy duty clutch.  !.5" is correct for my car and corvettes in 66.  I have the correct 66 eaton clutch not an aftermarket clutch.  The only difference I noticed between the std and hd aftermarket clutches was the mounting distance.  There is also a way to modify the Eaton clutch so that Iit will engage  earlier. 

When going down the road I don't think there is much difference.  When going at slow speed or at idle, the clutch as I understand is suppose to engage and travel at a speed more closely to the water pump according to  the hotter the radiator the more engagement of the clutch.  

As It stand now I will wait until the summer to see if I should adjust my clutch or possibly try a different pitch. Just thinking a 34.5 degree pitch fan will move a lot more are at idle than the 26 degree pitch.  Jut doing my research when there is 2' of snow in the yard.



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Jim L

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