Interesting, for the above engine using the calculation of the time for theoretical hp for a 4 cycle combustion engine, bore 6.75 x 6.75 x stroke 7.5 x rpm 1000 divided by 18000 then times 4 cylinders =75.93hp , not that far off the developed hp being 60, frictional loses not that great, also get a displacement of about 1074 inches, that's if my calculations are correct???.....can't imagine the foot pounds of torque it would develop at 1000rpm!