How do you tell the difference in a 2000 Chevy 5.3 and 5.7?

The easiest way to tell the difference between a 2000 Chevy 5.3L and 5.7L engine is by looking at the engine block casting number. This number is usually found on a flat surface of the engine block, often near the front, and will be stamped into the metal. You'll need to look it up in a GM parts catalog or online database to determine the displacement.

Visually distinguishing them is difficult and unreliable. While there *might* be subtle differences in the intake manifold or other accessories, these can vary due to trim level, options, and even manufacturing variations within the same engine size. Relying on visual inspection alone is risky and likely to lead to a wrong conclusion.

In short: The engine block casting number is the only definitive way to be sure.