Small Block

Chevrolet produced two types of crankshafts, forged steel and nodular iron. A simple way to identify them is by checking the parting line. This line was a result of the two halves of the crankshaft mold that produced the crankshaft itself.  On a nodular iron unit this line is about 1/32-inch wide and is raised above the surface. The forged steel line is anywhere from 1/4-inch to 1/2-inch side and is essentially flush.

Chevrolet generally used the nodular iron unit on engines with low to medium horsepower ratings and the forged steel in  engines with higher horsepower ratings.

The casting number is located on the rough surface of one of the counterweights or between the bearing journals. See the chart for casting number identification.

265 - 1955 through 1957 The 265 crankshaft is forged steel. The flange was carried over to the 283 crankshaft.
283 - 1957 through 1967 The 283 crankshaft was basically unchanged from 1957 through 1967 although different materials were used, nodular iron and forged steel, based on the application. All were a 3.00-inch stroke and have 2.00-inch rod journals and 2.30-inch main journals.
302 - 1967 through 1969 The 1967 302 crankshaft was a small journal (2.00-inch rod journals and 2.30-inch main journals) while all 1968-69 302 crankshafts are large journal (2.10-inch rod journals and 2.45-inch main journals) and all were 3.00-inch stroke. All are forged steel and Tuffrided.
327 - 1962 through 1967 All 1962-67 327 crankshafts are forged steel and have 3.25-inch stroke with 2.00-inch rod journals and 2.30-inch main journals. 1962-1964 'small journal' 327 crankshaft.	Early (1962-1964) flange design. Late (1965-1967) flange design.
307 - 1968 through 1973 All 1968-73 307 crankshafts are nodular iron. This is interchangeable with the 1968-69 327 crankshaft; only difference is the flywheel flange shape. All 307 crankshafts were 3.25-inch stroke with 2.10-inch rod journals and 2.45-inch main journals
327 - 1968-69 This crankshaft is a large journal and made in both cast iron nodular and forged steel. All 300HP and below engines received the cast iron crankshaft, others are forged steel.  Same basic design as the 307 crankshaft with 3.25-inch stroke, 2.10-inch rod journals and 2.45-inch main journals.
350 - 1967 through 1969 The only large journal crankshaft used in 1967 as was exclusive to the SS350 Camaro and is forged steel. The 1968 & 1969 crankshafts were available in both forged steel and cast nodular iron and have 3.48-inch stroke, 2.10-inch rod journals and 2.45-inch main journals.

W-Block

348/409 - 1958-1965 All 348 and 409 crankshafts are forged steel.

Big Block - Mark IV

396/402/427 - 1965 through 1972 The 396 crankshaft is the same as the 427 crankshaft except it is lighter due to the counterweight design. The third counterweight on a 396 crankshaft is 3/4" wide, the 402 is 7/16" wide, and the 427 is 7/8" wide. Prior to 1968 all 396 crankshafts were forged steel. In 1969 the lower horsepower engines used a cast iron crankshaft and have 3.76-inch stroke, 2.20-inch rod journals and main journals were different sizes; journals 1 thru 4 are 2.7475-inch while journal 5 is 2.7488-inch. All 1965-1967 427 crankshafts were forged steel. For 1968 & 1969, only high performance 427s used a forged steel crankshaft where low performance 427s used a cast iron crankshaft.
454 - 1970-75 The 454 crankshaft has the same flange as other big block crankshafts but is totally different in design. Unlike the 396/402/427 crankshaft, the 454 crankshaft is externally balanced at the front damper and flywheel flange. The 454 crankshaft has a 4.00-inch stroke but the same rod an main journal size as the 396/402/427.