Radiators

A radiator passes the heat that the coolant has collected in the engine into the air flowing through its core. A performance radiator adds capacity over the factory unit, usually with a deeper all-aluminium core. The radiators listed include vehicle-specific aluminium units, universal race radiators and radiators for engine swaps.

Heat rejection depends on core area, the temperature difference between coolant and air, and how much air passes through the fins. A deeper core adds tubes, but each extra row meets air already warmed by the rows ahead, so the gain shrinks with depth and the fan works harder. Where there is room, a larger frontal area is usually the more effective way to add capacity.

Many factory radiators have plastic end tanks crimped onto the core, and heat cycles eventually harden the seal or crack the plastic. An all-aluminium radiator removes that weak point. In a dual-pass design the coolant crosses the core twice, which speeds it through the tubes and helps heat transfer, provided the pump can drive flow through the longer path.

Start with the version made for the car, then decide on capacity.

• Gearbox: some radiators come in manual and automatic versions. The automatic version often carries the gearbox fluid cooler in its tank.
• Capacity: a thicker or larger core adds capacity, but it needs good ducting and fan cover to pay off.
• Universal radiators: listed by size, such as a 26 × 17 × 3.5-inch dual-pass race radiator or a 31.0 × 19.0 × 3.0-inch circle-track radiator. Drag-race radiators are built around short, full-load runs.
• Engine swaps: full-size and half-size radiators for swap layouts trade capacity against space.

Flush the old coolant and loose deposits out of the engine and heater before filling, so they cannot settle in the new core’s narrow tubes. Use a coolant with inhibitors suited to aluminium and renew it on schedule, because a system of mixed metals relies on that inhibitor against galvanic corrosion.

Mount the radiator on its rubber isolators and keep hose and bracket loads off the tanks, as vibration can crack aluminium at stress points. Hot air also needs a way out: a sealed duct to the core helps only if the air behind it can escape through the bonnet, wheel arches or underfloor. Pressure-test the system after fitting and check every hose joint warm and cold.