Try:

((bore / 2)^2 * pi) * stroke * cylinders = displacement

so...

((3.5625 / 2) + 0.04/2)^2 * 3.1415926) * 3.9375 * 6 = 240.81 cubic inches

Back in the early fifties, many 235s were bored 3/32" (0.09375") to give 248 cubic inches.