cu in ); bore x stroke : 81.0 by 95.5 millimetres (3.19 in × 3.76 in), stroke ratio : 0.85:1 - undersquare/long-stroke, 492.1 cc per cylinder , compression ratio : 18:1 (103 kW), 16.5:1 (125 kW) cylinder block & crankcase grey cast iron ; five main bearings , die - forged