Cars got bigger and were more luxurious. With Aluminum low in availability, carmakers when back to steel for pistons and other components. The increased weight resulted in heavier crankshafts and connecting ends and that worked its way down the rest of the car.
After the war things picked up for the auto-industry. While many countries were still picking up the pieces and rebuilding, the auto industry made huge strides forward in terms of volume, technology, design and overall innovation. The back half of the 1940s had cars created from odd parts left from the war as well as ground up machines that took advantage of the newfound consumer optimism and were made by re-energized carmakers.