With the fenderwells missing, you've created a huge high pressure ares in your engine bay.
The air from the front of the rad can't flow into this big pressure area. Those areas are equalized.
You need to create a low pressure area below the rad so all that high pressure air has a place to flow to.
You do that with an air dam installed right below the rad. The area behind the dam becomes a low pressure area.
There's one in this link.
Easy to build. I made one from plexiglass once.
http://www.thirdgen.org/forums/cooli...2-airdams.html