Truth be told, there is no such thing. The term “four core” has been misused for decades and accepted for generations. One reason is that very few people know how a radiator works and even less people know how they are made.
The term “core” is used to describe an assembly of parts. This assembly consists of tubes, fin, headers, and side plates. All these parts are brazed together to create the core. A radiator core can be made in several different configurations and materials. It could be made with copper or aluminum and each layer consist of a group of tubes and fin. The number of tubes in each layer can vary based on the material and application. In this case the term “four” is referring to the number of tubes in each layer.
This image is what most people would call a four-core. When actually there is only one core in the photo. What they are referring to is the number of “tubes” in each layer. The correct term used by most radiator professionals is a “four row”, referring to the number of tubes. Copper radiators have become obsolete and replaced with aluminum material.
Aluminum radiators created even more confusion because the design concept changed. The tubes in aluminum radiators tend to be much wider than the older copper units. This provides more contact surface and less dead space between the tubes. The height of the fin in aluminum radiators is also much shorter and that will result in more layers in the same given space. As a result, an aluminum radiator with two rows will exceed the heat rejection of a copper radiator with four rows.
This radiator uses two rows of 1” wide aluminum tubes. All aluminum cores are furnace brazed and they are 100% aluminum material. This eliminates the insulating effects that solder (lead) had in the older copper units.
The multi-slotted plate that all the tubes fit into is the “header”. Perpendicular to the header is the side plates or end sheets. It is the collection of the two headers, fin, side plates, and tubes that make up a core. So, the correct term for the aluminum radiator shown above is a “two row” and this design will perform better than a four row copper unit.