The LS-series engine (mine is actually an LQ4) has a small steam port that needs to be plumbed (arrow) to the radiator. This helps reduce hotspots by eliminating air bubbles. I had forgotten about this; otherwise I would have had a fitting added to the radiator. The crew at Pacific Fab stepped in and tapped the upper tank and added the fitting for me. The Be Cool tanks are made of thick aluminum and are fully welded (no glue like some cheaper alternatives), and as such, the fitting had a solid base to attach to.