What size is the crank journal on a 350 Chevy?
On a typical 350 small-block Chevy, the rod journals are 2.10 inches in diameter and the main journals are 2.65 inches in diameter. This article explains what those numbers mean, why they matter for bearings and clearances, and how to verify them when rebuilding or modifying a 350 engine.
The question focuses on the specific diameters of the crankshaft journals in a 350 Chevy. Because there are stock variants and aftermarket alternatives, it’s important to distinguish between the rod journals that the connecting rods ride on and the main journals that sit in the engine block bearings, as well as to note that some performance cranks use different sizes. The sections below lay out the typical sizes and how to confirm them for your build.
Common journal sizes in a 350 small-block Chevy
This section lists the standard sizes you’re most likely to encounter in stock or mildly tuned 350 builds. Always verify your exact crank and bearings from the manufacturer or a detailed spec sheet, especially if you’re using aftermarket or stroked cranks.
Rod journal size
In the 350 small-block, the rod journals are typically 2.10 inches in diameter (53.34 mm). This is the diameter of the bearing surfaces the connecting rods rotate on.
- Standard rod journal diameter: 2.10 inches (53.34 mm).
- Note: Some aftermarket or performance cranks may use different rod journal diameters; always verify the exact specification from the crank manufacturer.
When rebuilding, match the rod bearings to the rod journal size and check for wear or scoring that could affect clearance and oil flow.
Main journal size
For a typical 350 SBC, the main journals are normally 2.65 inches in diameter (67.31 mm). These are the surfaces the crankshaft mains spin in within the block.
- Standard main journal diameter: 2.65 inches (67.31 mm).
- Note: Aftermarket or performance cranks may use different main diameters; always verify with the manufacturer or bearing catalog.
Bearings for the main journals must match the crank’s main journal size; if the crank is ground or replaced with a different spec, the bearing size must be adjusted accordingly to maintain proper clearances.
How to verify your exact journal sizes
Because engines can vary by year, model, and aftermarket modifications, it’s essential to measure and confirm the exact dimensions before ordering parts or starting a rebuild.
- Prepare the engine and access the crank journals with proper tools and precautions.
- Measure rod journals with a micrometer across multiple points to determine average diameter and roundness; typical standard is around 2.10 inches.
- Measure main journals with a micrometer in the same way to determine if they’re at standard 2.65 inches or have been altered.
- Consult the crank manufacturer’s specifications or bearing catalogs to select the correct standard or undersized bearings based on your measured sizes.
- If you’ve had the crank ground or replaced it with an aftermarket piece, ensure the bearings, rods, and pistons are compatible with the new dimensions and clearances.
Accurate measurement helps ensure proper oil clearance, bearing life, and overall engine reliability during startup and operation.
Summary
For a typical Chevrolet 350 small-block, expect rod journals of 2.10 inches in diameter and main journals of 2.65 inches. Always verify these dimensions for your specific crank and build, especially when using aftermarket or stroked cranks, and verify clearances with the proper bearings. Accurate measurements and correct bearing selection are essential to a reliable rebuild.
What is the journal size of a small block Chevy?
2.100 IN
GTIN: 00193564266231
| Rod Type | I-Beam |
|---|---|
| Center To Center Length | 5.700 IN |
| Average Gram Weight | 676 GR |
| Pin End Bore | 0.927 IN |
| Journal Size | 2.100 IN |
What is the diameter of the crankshaft journal?
Stock journal diameters are: 1.8758/1.8764" and 2.1265/2.1270" respectively. There are no bearing ID specs available, as they are designed to crush slightly when the caps are torqued down. That's why the only way to determine actual bearing clearance is with Plastigauge or an equivalent product.
What size is the main journal on a 350?
The main journal size for a standard 350 Chevy engine is approximately 2.45 inches in diameter. The rod journals are a smaller 2.10 inches in diameter.
- Main journal diameter: 2.452.452.45 inches (62.2362.2362.23 mm)
- Rod journal diameter: 2.102.102.10 inches (53.3453.3453.34 mm)
- Other specifications:
- Stroke: 3.483.483.48 inches
- Bore: 4.004.004.00 inches
What size is the crank bolt on a Chevy 350?
The crank bolt for a Chevy 350 is most commonly a 7/16-inch fine thread (7/16−207 / 16 minus 207/16−20), typically 2.25 inches long, with a 6-point hex head. However, the bolt may differ depending on the specific engine and accessories, and some aftermarket or big block applications might use different sizes, like 1/2-20. It's crucial to confirm the size for your specific engine and application before purchasing a replacement.
Common bolt specifications
- Thread size: 7/16−207 / 16 minus 207/16−20 (fine thread)
- Under-head length: 2.252.252.25 inches
- Head style: 6-point or 12-point hex
- Material: Grade 8 steel is recommended for strength
This video shows how to remove the crankshaft pulley and harmonic balancer on a Chevy 350: 58sThe Burnout ShowYouTube · May 4, 2023
Important considerations
- Confirm your application: While 7/16−207 / 16 minus 207/16−20 is standard, some applications or aftermarket cranks may use a different thread, such as a 5/85 / 85/8 inch socket size on a larger bolt. Always verify the size for your specific engine.
- Check accessories: The length of the bolt can vary depending on the number and type of pulleys being used. Aftermarket pulleys, especially aluminum ones, may require a longer bolt.
- Use the correct tools: A 6-point or 12-point socket is necessary to prevent slipping. Using a specialized harmonic balancer installation tool is recommended for proper and safe installation.
