Well there is part of your problem
4 row rads are old tech the 4th row will actually transfer heat back into the 3 row making them both pretty much useless.
Modern trend is to use 1 or 1 1/4 inch tubes for only 2 rows
I have had several 2 row they cool very well
Look at Griffin radiators they are made in the USA and work very well
Are you sure your lower rad hose is not collapsing at cruzing rpm?
