Aluminum radiators transfer heat more efficiently than brass cores do. That's Griffin's reasoning behind how they build, and I've heard good things about them.

Another cause, and it's been brought up about the 3.5 DOHC's is that the water pump doesn't move a whole lot of volume. I wonder if the inlet vs. outlet temps on your present set-up is acceptable, but there just isn't enough coolant getting through. Just a thought.

John B.

'87 Raider 2.6 Turbo Auto, Under Construction
'95 Montero SR, 35x12.5/15 BFG M/T KM-2's, Rock sliders, Qtr panel chop, gas tank lift, 2" BL, Aisins, 5.29s
'95 Pajero Mini
'98 Montero Winter Ed.
'04 Cadillac XLR
'03 Kawasaki ZRX1200R
'60 Ford Falcon 4Dr