Well i got the tropical fan back in except the two bolts between the rad and the firewall...during a 104 degree day.

I put the downty fan on at the beginning of the summer. But every time I go for a drive into hangman Canyon (To exit it’s 4 miles uphill) and I always watch the temperature gage go up and up and up until it’s almost on red. Once I even had to stop and wait for it to cool down. With the tropical fan I never had any problems. And it’s only when I drive uphill for long distances That the downty fan is problimatic. I guess changing the fan again is in my future.  And noise is not an issue.  Even though I run a SuperTrap it’s still not as loud as a Harley. 

A tropical 6-blade fan will move huge amounts of air, though I believe the older 4-blade will move more (two 2-blades at 90°).  Both are very noisy, and the tropical sounds like a turbine.

The Dowty has the advantage of the moving blades to compensate for increased air flow at theoretically higher road speeds, though that is in reality rpm dependant.  Either way, it saps less power and won't cavitate thus increasing its efficiency.

I'd say the tropical will move more air all the time. While I have one of the other I don't think I'd use it. I removed it from a engine that suffered a spun main and a cracked head. Not blaming the fan just turned out that way. Steve (CTR)

Which one will push more air??

I’m hoping Alex will see this