Fan size

[sirstude]

Hi all,

I am going to change the fan on my Impala.  Putting in a new radiator, (the old one sprung a leak) with a factory shroud from a 1967 427 car.  I am going from a 3 core to a 4 core with extra water capacity, some day I might finally get AC in this thing.  

How much room should there be between the blades and the opening in the fan shroud.  The shroud has about an 18.5 inch opening. A 19 inch Flex-A-Lite steel race fan just fits, but has no clearance, and this is with just a bench test, not mounted.  I am wondering if I should use a 17 or 18 inch 6 blade fan.  I am leaning to the 17 inch fan, in case of engine movement.  

The stock setup is a 4 blade 14 inch fan.  The only time I ever have any heat issues at all is in parades.    I just want to get the most out of the shroud.

Thanks
Doug

[parklane]

I would think that you need at least 1" all around because of engine movement etc., but Frank will know for sure.

John

[enjenjo]

I would say at least 1/2" between the fan and shroud.  1" would be about the limit to have the shroud be effective. I have been buying six blade, fixed blade, steel, racing fans, made by AllStar racing. They have been very effective.

[sirstude]

Frank,

That is what I thought also, I am thinking if I go to the 17" there will be about an inch and a quarter or so , so will probably go with the 18.  I will look up that Allstar fan.  Are you buying them localy or over the net?

Thanks
Doug

[enjenjo]

I get them locally through Lane Automotive.

[Crosley.In.AZ]

lots of air movement is good for the radiator

[Mr Cool]

With the race cars we had to make sure that air would only be sucked through the radiator, any gaps between the rad and shroud would affect the cooling system too.
Another one that worked well was to ensure all air going into the radiator would not be diverted around it, that meant using rubber filler strips between the rad and surrounding metal, including the bonnet (or hood for you 'merricans).
Every little bit makes a difference, and with the racecar it was very noticable.
I didnt use a fan at all for a long time on the roundy, as I believed it to be using power to drive it and that cost me lap times, until I got stuck one day without it, and nearly cooked the engine. Been using one ever since..