Abstract: A heat exchanger core having a plurality of spaced fluid conducting tubes operatively connected in series at their upper ends by projecting tank portions. The tubes have flattened main body portions that extend downward from the tank portions to terminal ends having rows of integral spacing and locking links formed with snap fasteners for releasably locking onto one another to connect the lower end of the tubes to one another providing column strength thereby preventing damage to corrugated metal air centers disposed between adjacent tubes by compression forces exerted on the core. In addition to the spacing and locking links, this core features integral snap fasteners to lock the separate plates of each tube together in face to face relationship so that the entire core is mechanically connected and interlocked and is ready for permanent connection by brazing.