The math is:
Bore x Bore, or Bore Squared 4.28" x 4.28" = 18.3184"
x 4.375" stroke = 80.143"
x 3.14159265359 (Pi) = 251.77666
x2 = 503.55"
Or in the case of using a 4.50" stroke crankshaft it would be:
Bore x Bore, or Bore Squared 4.28" x 4.28" = 18.3184"
x 4.50" stroke = 82.4328"
x 3.14159265359 (Pi) = 258.9702789
x2 = 517.94055578"
Tom