What CFM is needed to keep engine cool?

[doubletrouble]

I am thinking about switching to electric fans and am wondering what CFM rating i need to go with to keep engine cool when driving around town on the highway and when crawling? I am almost done switching to TPI and I need a little more room up front for my air intake. Trying to decide if I should go with electric fans or get a spacer for my stock fan? Thanks

 

[Hogback Fabrication]

What motor? What truck? What radiator?

 

[doubletrouble]

What motor? What truck? What radiator?

'77 Blazer with a 350 and a auto tranny, its the tall 4 row radiator just replaced it.

 

[4X4HIGH]

Safely 2800 cfm should keep you cool.