There isn't a single definitive answer to who makes the "lightest" V8 engine. The weight of an engine can vary significantly depending on the materials used (aluminum vs. iron blocks and heads), the specific application (racing vs. road car), and the displacement. Manufacturers constantly refine their designs, so what's lightest one year might be heavier the next.
To find the lightest *currently produced* V8 would require extensive research across all manufacturers and their model lineups, comparing specs which aren't always readily available. Lightweight V8s are often found in high-performance applications, and that information is sometimes proprietary.
