D = π(bore / 2)² · stroke · n
can be rewritten as
D = π(1/2 * bore)² · stroke · n
If bore = k /2, and stroke = h, and # of cylinders = n = 8, then
D = π(1/2 * k/2)² · h · 8
= 8π*h(k/4)²
= 8π*h(k²/16) since (k/4)² = k²/4² = k²/16
= π*h*k²/2
Answer for the first part: D = π*h*k²/2
For second part, if bore = 4 inches, stroke is 3.4 inches, and # cylinders = n = 4, then
D = π(1/2 * bore)² · stroke · n
D = π(1/2 * 4)² · 3.4 · 4
D = 170.9 cubic inches