Cubic Inches
The formula for cubic inches is: Pi x radius squared x stroke x number of cylinders.
(radius is the bore/2)
A 283 has a 3.875 bore and a 3 inch stroke.
(((1.9375 x 1.9375) x 3.1416) x 3) x 8= 283.038525
Same as above but it is easier for me to use and visualize.