CFM's Needed for 4.0

Guy's I'm just wondering if anyone know the CFM's the mech. fan is putting out along w/ the aux. electric when it's on? Or if you can tell me what the 4.0L needs as far as CFM's to keep it cool & back it up w/ proof that would be good also.

If you find anything of value, crossing-posting to other boards, would you let us know?

I keep thinking I need to borrow an airflow balancing hood and snug it up to the grill to provide an idea of the cooling system airflow with a locked clutch and electric fan.

BTW, why do you ask? What is the project?

I'm looking into swaping the mech. fan & the electric aux fan to a dual electric setup where the one fan will cool as a main then the second will kick in after a certain temp. SPAL has a dual 11" setup that pulls 2780 cfm & i'm wondering if thats enough to cool the engine.