Here are the engine options for the 2004 Volvo XC70:
* 2.5L 5-cylinder: This was the base engine for the XC70 in 2004. It produced 168 horsepower.
* 2.5T 5-cylinder (turbocharged): This engine was available as an optional upgrade, offering 208 horsepower.
Therefore, the base engine size is 2.5L.
It's important to note that the specific engine details might vary slightly depending on the exact trim level and region where the car was sold.