When I was building small block engines for a local round track with a carburetor CFM limit, I came up with a bore/stroke combination that showed all 305 cubic inch casting numbers during a tech line inspection, but actually had a CID of 255. Most of the competition was running 350's with a .030" overbore, for 355 cubic inches. My engines could run more than 1,000 RPM faster on the same carb, so if my guy ever got out front, there was no catching him. As an added benefit, my engines sounded like a bumblebee on steroids, and nothing but a complete disassembly would reveal what was going on.
It was a lot of fun, beating a bunch of guys with 100 cubic inches more engine!
Jerry
