When it comes to the difference in performance between copper/brass and aluminum radiators you may find the tests by U.S. Radiator surprising. They found that temperature drops at all operating ranges was virtually the same, with a slight advantage going to the copper/brass unit. But consider this: the thermal conductivity or heat transfer rate of copper is 92 percent versus aluminum at 49 percent. However, the copper fin is bonded to the tubes or water passages using lead solder, which is very inefficient and slows the heat transfer rate to just slightly better than that of aluminum. This can be a disadvantage if the bonding process doesn’t allow the copper fin to touch the brass tube and why not all copper/brass cores of similar design but different manufacturers transfer heat equally. Copper/brass radiators because of their weight and durability have been around a long time and are easily disassembled and reassembled for cleaning purposes. Not the case with aluminum unless speaking of the OE version that comes with crimp-mounted plastic tanks. As a result the life expectancy of the aftermarket aluminum radiators will be far less than that of copper/brass.

The Triple flow Option

This unique design re-routes the coolant back and forth through the radiator core multiple times. As a result, the coolant travels further through the core and is exposed to more airflow and coolant temperature can be dropped 15-20 percent.

Cooling System FAQs Courtesy of U.S. Radiator

Q What are recommended engine-operating temperatures?

A Most hobbyists aren’t concerned with fuel efficiency so our recommendation would be 175 to 195 degrees F. Higher operating temps will burn fuel more efficiently but the increase in operating pressure and metal distortion can easily create problems over time.

Q Do you recommend internal or external transmission coolers?

A External transmission coolers are preferred to keep unnecessary heat out of the radiator.

Q How does radiator core thickness effect cooling?

A An increase in thickness over a stock application allows for greater fin bond surface and therefore greater temperature drop. When going from a two- to a four-row, for example, you double the fin bond or heat transfer points. The increase however isn’t one to one because the transfer efficiency of the trailing rows is adversely affected by the increase in air temperature from the previous rows and the decrease in air velocity caused by the increased thickness.

Q Do you recommend mechanical or electric fans?

A We always say, why rely on another operating system if you don’t have to? Mechanical fans turn when the motor turns. However, we highly recommend a shroud properly fitted to the fan and radiator. The only time you really depend on a fan is at idle or low speed where there is little or no air flowing through the grille. Shrouds are necessary to maximize the amount of ambient air being pulled through the grille and radiator. For the record, proper fan and shroud alignment should be leading edge one-third in and trailing edge of the fan two-thirds out. The airflow off the back of the fan deflects at about a 45-degree angle when set this way. When the blade extends further into the shroud the air off the back of the blade flows straight back into the block and decreases the airflow efficiency by about 15 percent.

That being said, if an electrical fan is the only way to go then by all means place it on a shroud that covers the entire core. We often see an electric fan attached directly to the core and the only thing this does is waste the rest of the core surface when you need it the most. A 16-inch electric fan attached to a core only cools a 16-inch circular section of that core. Where space is an issue, U.S. Radiator offers a 3/4-inch-deep aluminum shroud that enables adequate airflow over the entire core and when combined with a thin-line electric fan results in a total depth of 2-3/4 inches.