Join Date: Sep 2000
Location: Washington, Michigan USA
Some of the multiple electric fan setups work great around town, but the extensive shrouding actually restricts airflow at highway speeds. Water pumps are hardly ever part of a cooling problem, regardless of the marketing hype, and a "high-flow" pump can actually make it worse by moving coolant too rapidly through the radiator so it can't reject the heat fully in one pass.
Assuming your hoses are in good shape (and the lower one isn't collapsing under suction due to the reinforcing spring wire being corroded away) and your thermostat is operating properly, all that's left is the radiator, shroud, and fan. The radiator should be sealed to the rad support so the air is forced to go through it, not around it, the factory shroud should be intact, and a functioning factory-type clutch fan is far better than a flex-fan. The correct fan clutch will place only the front half of the fan blades inside the shroud for best efficiency.
If all this is in place and you still have a cooling problem, especially at highway speed, it's the radiator not having adequate cooling capacity. Old copper/brass radiators build up scale and corrosion inside the tubes (especially if anti-freeze hasn't been kept fresh - changed every two years - and used at a 50-50 mix), which acts as an insulator and drastically reduces the heat transfer from the coolant to the air flowing over the tubes and fins. Usually they can be rodded-out, or re-cored, to restore their original heat transfer efficiency. If not, the aftermarket aluminum radiators will normally provide the required cooling capacity, although they need proper fans and shrouds too, or they won't be able to do the job around town. Proper anti-freeze is even more important with an aluminum radiator in order to prevent corrosion, as they can't be reliably repaired if they develop corrosion leaks.
The original factory fan/shroud/radiator design resulted from a lot of development work, and they work well; generally problems begin when people start modifying them or removing or substituting the correct pieces with other stuff that isn't part of a "system". Before you spend big bucks for an aluminum radiator, make sure the stock system is in proper working order, and is as it was designed to begin with, not a collection of catalog stuff with miracle advertising claims that wasn't designed so all the pieces work together as a system.
'69 Z28 Fathom Green