* 6.2 liters is the engine's displacement – the total volume of all its cylinders. This is a relatively modern engine size.
* 390 cubic inches (often shortened to just "390") is also an engine displacement, but using a different unit of measurement (cubic inches). It's an older engine size, common in classic Ford vehicles from the 1960s.
To convert cubic inches to liters, you need to multiply by approximately 0.0164. A 390 cubic inch engine is roughly 6.4 liters. Therefore, while similar in size, a 6.2 liter engine is slightly smaller than a 390 cubic inch engine.
