All models come with a one piece seal that fits into a housing attached to the block. The crankshaft must be installed first and the crankshaft bearing caps bolted in place, then the new seal should be installed in the housing and the housing bolted to the block. Prior to installing the seal and housing, the seal contact surface should be carefully inspected for scratches and nicks that could damage the new seal lip and cause oil leaks. If the crankshaft is damaged, the only alternative is a new or different crankshaft. The old seal can be removed from the housing with a hammer and punch by driving it out from the backside, supporting the seal retainer on two wood blocks and carefully driving out the seal. It's important to note how far it's recessed into the housing bore before removing it; the new seal will have to be recessed an equal amount. Care should be taken not to scratch or otherwise damage the bore in the housing or oil leaks could develop. The housing should be clean before applying a thin coat of engine oil to the outer edge of the new seal. The seal must be pressed squarely into the housing bore, so hammering directly on it is not recommended. If a press is not available, the seal can be tapped into place with a hammer and a block of wood. The block of wood must be thick enough to distribute the force evenly around the entire circumference of the seal. Work slowly and ensure the seal enters the bore squarely. The seal lips must be lubricated with moly-base grease or engine assembly lube before the seal/housing is slipped over the crankshaft and bolted to the block. A new gasket is needed-no sealant is required-and the dowel pins must be in place before installing the housing. The bolts should be tightened a little at a time to the torque.