Electric fan install help.

The problems boil down to the wrong fans and shrouds.

The problem with fan ratings is that they are all free flow ratings because those are the flow highest numbers and look the best. But radiators will have significant pressure drop (up to 1"or 1.5" H2O, which is a lot for fans) at any really usable air flow rate, and the cheapo fans' flow rates will just drop into the toilet with that level of pressure drop. But there is nothing on the distributors' or even manufacturers' websites that show the actual flow rates versus pressure drop, so us amateur auto designers have nothing to go on. That data is standard stuff for electronic cooling design but does not seem to be anywhere to be found for these auto fans.

If you want to see how 2 fans can flow a lot differently when installed, here is an illustration. http://www.omafra.gov.on.ca/english/engineer/facts/06-057.htm

Even though these fans are for farm buildings, the principles are always the same. The graph about 2/3 of the way down the above page (Figure 6) shows 2 fans' flow versus pressure curves. Look at the upper solid line and compare it to the lower dashed line.
- Fan A flows 7500 cfm at 0 pressure and over 5000 CFM at .3" pressure, a drop of 30%.
- Fan B flows 5000 cfm at 0 pressure but only 1500 cfm at .3" pressure, a drop of 70%.

Even if you scaled up fan B to flow 7500 cfm at 0 pressure to equal the free flow of fan A, it would only flow just over 2000 cfm at .3" pressure. This shows what is going on with the poor auto cooling fans; their flow just goes to crap behind the pressure drop through a radiator.