S&amp,S Cycle S&amp,S Standard Bore Engine Cases 31-0010 Cast from A356 T-6 heat-treated aluminum alloy Include crankcase bolts, washers and nuts, cylinder mounting studs, timing hole plug, magnetic drain plug, assorted breather and oil line fittings, top end oil screen spring and plug, sprocket shaft Timken bearing assembly, oil seal, pinion shaft main bearing race, cam needle bearing assembly, oil pump shaft bushings and installation instructions Use Timken style sprocket shaft bearings and 1958 and later pinion bearings (will not accept 1957 and earlier flywheels) Bearing races are all line honed and breather cavity is precision machined to optimize breather timing for maximum oil scavenging Machined for 3.4375in. cylinders and tapped 1/4in.-20 for gear covers, oil pump, tappet guides, timer and timer advance