From what I’ve been told, is that the roller bearing crank engines needed to be driven hard, as a sport car, keeping the rpms up to satisfy the flow of oil to the crank. Wide open roads, less prolonged stops. When the roller crank equipped cars arrived in the US, the new owners drove them casually in American stop and go traffic, with low idle rpms, and the small oil pump could not keep up, often starving the cranks need for oil. The cranks were failing or rattling at 10k miles due to this. However, knowledgable drivers knew that if you simply kept the revs up while driving in traffic and sitting at stop lights, the cranks would be reliable and give you good service. Many engines were converted to one piece cranks because of this, and the removed roller cranks became wall hangers and door stops. Now however, serious purists restoring their cars back to factory, realize that the roller cranks are a part of original design, and want them reinstalled as part of the rebuild, knowing that they have to be driven and cared for in a certain manner. Unfortunately, very few people can properly rebuild a roller crank today, and when they failed back in the 50s, the factory had to rebuild the crank, often at the cost of up to a grand.