[george kujanski]

Let's review what we have found during the course of this discussion:

To cool better we need to:

1. Create less heat: make the engine run as efficiently as possible, timing, mixture, etc.

2.Improve coolant flow: efficient pump, remove blockage, reduce restrictions, i.e. high flow thermostat.

3. exchange heat from radiator to air: more radiator surface area, and more airflow.

Now I'll make the assumption that a 4 row radiator has better flow characteristics since there is an extra row of tubes, therefore at the same pressure differential more flow thru the radiator. Also, since it is larger, there is more surface area, which improves heat transfer to the air. So that is a Good Thing (thanx Martha).

A smaller pump pulley would increase flow rate so that is a Good Thing also, but finding pullies & belts is not as easy...

A high flow thermostat would also help flow rate.

A clutch fan helps because it creates less drag (less wasted power) at high speed, where there should be enuf airflow thru the radiator anyway, and if the air temp thru the rad. is high enuf, it automatically increases air flow.

A shroud also helps at low vehicle speeds because it takes the max airflow created by the fan and passes the air over more of the surface area of the radiator (than without a shroud).

In fact, isn't a fan with a shroud similar in action to optimizing the clearance to the pump vanes (less leakage aroound the impeller)?

This all is assuming that attempts at increasing flow rate isn't limited elsewhere by constrictions in cooling jackets, cavitation, etc.

that's the way I see it.....

George