I had dozens of cars with Flex fans and AC and they did not overheat. You must use the appropriate fan shroud for the fan or fans being used or like you know it may not be efficient. If you still have the flex fan and the shroud spacing is correct I would stick it back on and test it. Unless you had issues with heat with that fan. The flex fans I use are original equipment Ford flex fans. Like this one. I drill holes in them to fit the Chevy bolt pattern. https://www.ebay.com/itm/FORD-CF-D8...606891?hash=item1ce48e2beb:g:PZUAAOSwwRReUWOs Notice the huge pitch of the blades and all the rivets in them. And notice the blades are offset ..That keeps them quiet. An even spaced fan will make a lot of noise. I have spun these to 8500rpm and never had a failure. I have ran them at 6500 rpm for over 15 minutes without a break.