Posted by Keith in Washington [24.41.55.51] on Monday, October 12, 2015 at 17:33:03 :
In Reply to: Re: Kaegi, Clueless, overheating, etc. posted by Keith in Washington [24.41.55.51] on Monday, October 12, 2015 at 10:37:21 :
Let me correct and add to my comment above.
First it is critical to have a correctly designed and fitted fan and fan shroud. Without a fan shroud air is only pulled through the radiator directly in front of the fan. With a fan shroud the air will be pulled through the entire radiator. The shroud needs to cover the entire radiator and be tight along the edges. The fan hole should tight to the fan with about 1/2" space between it and the fan blade tips. The shroud hole should have a lip on it. The fan blade tips should be placed about 50% into the fan shroud on a sucking fan and 33% on a pusher fan. Placement of the fan is critical for air flow. Too shallow into the shroud into the shroud the fan can not develop a good air flow due to a lot of turbulence at the blade tips. Too deep into the shroud and the fan cannot develop airflow again.
The stiffer the fan blade the better flow. Both rigid and flex fans can be very effective. Low speed or low engine rpm is where the fan needs to be most effective as forward movement of the vehicle is too low to force air through the radiator. That is why some people like flex fans as they pull the most air at lower RPMs and flatten out at high RPMs and suck less air. Rigid fans always pull air at all RPMs and tend to cost more in terms of fuel mileage. That is why they have thermal clutches so that they are not spinning when the engine is at normal operating temps. I personally do not like thermal fan clutches as the engine is well on its way to overheating before the fan kicks in.
I spent several years resolving overheating in my WC53 with a V8 and the original radiator. Through a succession of efforts I have gone from over heating at idle with an ambient temperature of 70 degrees to being able to slowing move through a parade route in 90 to 100 degree ambient temperature. Originally I did not have a shroud with a flex fan. Now I have the same radiator with a correctly fitted shroud with the same flex fan that has been correctly positioned into the shroud and an overflow tank. No other changes were made (no differences in water pump, piping or otherwise).