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This crankcase is machined to accept the stock oil filter assembly introduced on some 1992 model Big Twins. This convenient, accessible location can be utilized to simplify installation of an oil filter in custom applications. Machined to accept 84-91 or 92-99 style oil pumps and the stock 84-99 style oil distribution system. For Evolution style engines, the engine builder has the option of venting the crankcase breather from the crankcase, through the cylinder heads, or both. It's recommended using both crankcase breathers in engines of 96"or larger displacement. To make this possible in all applications, there are two crankcase breather holes available in the rear of the S&S® alternator crankcases. One is in the stock location and the other is angled down to allow the installation of a crankcase breather fitting in the chassis with integral transmission/oil tank. S&S® Big Twin cases optimize crankcase oil scavenging efficiency by using a ported design breather passageway and a breather window that is machined to maximum timing specifications. These features allow the air/oil mist to move smoothly from the flywheel cavity to the gear chest of the engine. The return oil pick-up passage to the return side of the oil pump has been relocated in order to avoid the turbulence caused by the oil pump drive gear. This unique design results in greatly improved scavenging of oil from the gear case and virtually eliminates oil carry over at 5 sustained high speeds. S&S® Big Twin crankcases for Evolution style engines are not machined with a primary oil scavenge port for drawing oil from a Shovel style primary chain case. If the primary oil scavenge port is required on an Evolution style crankcase, it can be special ordered.
99 Evolution Big Twin models: stock bore and natural aluminum; accepts 92-99 style oil pumps; 92-99 cases differ from the 84-91 only in the oil pump mounting bolt pattern.
91 Evolution Big Twin models: stock bore and natural aluminum; accepts 84-91 style oil pumps; 84-91 cases differ from the 92-99 only in the oil pump mounting bolt pattern.
84 Shovelhead style: stock bore; accepts 81-84 style oil pumps; machined for stock primary oil return.