Originally Posted by Cole
I am using a Zirgo 16 inch 3000 CFM electric puller fan on my radiator to cool the 350HO crate engine. Question is do you need a fan shroud? It is butted right up to the radiator so i am kind wondering if I still need one..
Update... Well after reading old posts the answer i guess is no...
Yes, but in your case maybe no difference in performance.
The purpose of a shroud when using a puller fan is that the fan alone only pulls air thru the radiator core in the area immediatly in front of the fan. The rest of the core is essentially not contributing to cooling the coolant. By moving the fan back a few inches and surrounding the radiator core with a shroud back to the fan, the fan then creates a low pressure area behind the entire core causing air to flow thru all of it rather than just the part in front of the fan.
A pusher fan is a bigger problem, as a shroud between it and the radiator doesn't change the flow pattern in any significant way so most air is blown thru the core in an area about the size of the fan blades.
The solution to a pusher configuration is multiple smaller fans that can cover more of the radiator's core surface. In the case of a close coupled puller fan such as yours, the solution would be the same, more but smaller fans pulling air thru more of the core area.
It is unfortunate that the advertisers want to talk about more CFM from a single fan with a more powerful motor, when the real solution is pulling air over more core area which will take several smaller fans.