* Journal Diameter: This is the most crucial measurement. Small-block Chevy crankshafts have specific journal diameters for the main bearings and rod journals. You'll need a micrometer to accurately measure these. Different generations (e.g., early SBC, Gen I, Gen II, Gen III, Gen IV) and even applications within a generation will have slightly different dimensions. Reference charts specific to the era and engine family are essential for this.
* Length: Measure the overall length of the crankshaft. This, combined with journal diameter, helps narrow down the possibilities. Again, reference charts are necessary because different stroke lengths will result in different overall crankshaft lengths.
* Number of Main Bearings: Small-block Chevys typically have a 4-bolt main bearing cap design for the mains. You can count these easily to verify if it's a 4-bearing.
* Counterweights: The shape and size of the counterweights are characteristic. While there's variation, you can compare them to known examples in pictures or diagrams. However, this is less precise than measurements.
* Casting Numbers: Look for casting numbers stamped on the crankshaft itself. These are often found on the counterweights or near one of the ends. A comprehensive small-block Chevy crankshaft identification guide, or a parts catalog, will allow you to decode these numbers.
* Rod Journal Size: Like main journals, you need to measure the rod journal diameter with a micrometer. The rod journal diameter is different from the main journal diameter and it’s critical for proper identification and compatibility.
Important Considerations:
* Accurate Measurement: Using a micrometer is absolutely essential for journal diameter measurements. A caliper might provide a rough estimate but is not sufficient for accurate identification.
* Reference Materials: You'll need access to charts or manuals showing the specifications for small-block Chevy crankshafts. These can be found in engine rebuilding manuals, parts catalogs (like those from Summit Racing, Jegs, etc.), or online databases.
* Modifications: A crankshaft might have been modified (e.g., resized journals, different stroke). This complicates identification.
In short, rely on precise measurements (journal diameters and overall length) combined with casting numbers and visual inspection to accurately identify a small-block Chevy crankshaft. Don't rely on just one feature.
