[ford38v8]

A peculiarity of the '36 radiator is its large flat upper tank, which is more vulnerable to expansion/contraction related failure than are radiators of other years, due in large part to the very shape itself. The use of a pressure cap on an unmodified '36 radiator is a prescription for disaster. Under pressure, the flat surface balloons out (oil cans if you will), causing the soldered seams to stress and fail.

During a recore of the '36 radiator, an inner support can be soldered across the flat, the goal of which being to offer some rigidity to that surface, and protection for the soldered seams, which themselves were never designed to survive the installation of a pressure cap.