Procomp Electronics 4340 Billet Steel crankshafts are manufactured from high quality true billet round bar stock. Their performance, strength and horsepower capabilities are significantly outstanding compared to cast forged crankshafts. An engine with a 4340 billet steel crankshaft will rev faster and cleaner due to the different harmonics produced from the high grade material. Those crankshaft are x-rayed and ultrasonically tested.