RPM International offers different types of crankshafts — 4130/5140 Forged and 4340 Forged.
SAE Certified 4340 forged material is used for superior strength and its proven performance in the aircraft and aerospace industries. For increased strength these cranks are given a second heat treatment after rough finishing and then Nitride-harden eliminating any deformation after leaving the factory. RPM 4130 / 5140 forged crankshaft are also perfect for the racer who wants a forged unit without the price of a full race crank. These crankshafts are made from SAE Certified 4130, 4142, or 5140 Chrome Moly materials and are Nitride hardened for superior strength. Please consult your price list or the RPM catalog for the most popular street/strip applications.