Cast crankshafts are typically used in low-horsepower applications. They are the least expensive to produce and wind up in all but high-performance vehicles. Steel crankshafts are capable of handling a lot more twisting force and higher rpm than a cast crankshaft. A cast-iron crankshaft is made in a mold, after which it is installed in a lathe and ground to specifications. A steel crank is forged and twisted and hammered into shape.
- Look at the counterweights on the crank. A large parting line with grinding marks on it is indicative of a forged steel crank. That is because it was forged and bent into shape.