http://www.sciencemadesimple.com/conversions.html

just select what you want to convert (Weight, Length, area, etc.). For engine displacement you would select "Volume"

On the next page, type the number you want to convert.

For instance - If you want to know how many CI's there are in 50 cc's type in "50" and choose Cubic Centimeters, and convert to Cubic Inches.

I keep that in my favorite places on ALL of my computers