LY5 engine upgrade guide

Intro to the LY5 Engines The LY5 came in GM trucks and SUVs in 2007-‘09 and made 320 horsepower right out of the box. It’s a Gen. 4 5.3L iron-block engine, so you’re getting the better intake manifold, connecting rods, and ECM. The engine also had 799/243 casting heads and 9.9:1 flat tops. 5.3’s don’t get