Connecting Rod Nut. (Note for DB4 only - Some earlier engines are fitted with a different bolt and nut, utilising a split pin as a means of locking. The earlier castellated nut must not be used with the later bolt and the later nut must not be used with the bolt that is drilled for a split pin. If the engine is fitted with the earlier type of bolt and nut and either component requires renewing, BOTH must be replaced by the correct parts.)