how to identify a 4 bolt main 350

Identifying whether a Chevrolet 350 engine has a 4-bolt main or a 2-bolt main is important for determining its strength and potential performance capabilities. A 4-bolt main engine typically offers more strength and stability, making it preferable for high-performance applications. Here’s how to identify a 4-bolt main 350 engine:

1. Check the Engine Block Casting Number:

  • The most reliable way to identify whether a 350 engine has a 4-bolt or 2-bolt main is to locate the engine block casting number. You can usually find this number on the side of the engine block, near the bellhousing area (where the transmission attaches). The casting number is often raised and can be a combination of letters and numbers.

2. Decode the Casting Number:

  • Once you’ve located the casting number, you’ll need to decode it. This will tell you the specifics of the engine block, including whether it has a 4-bolt or 2-bolt main. The casting number may look something like “3970010” or “14010207.”

3. Reference a Casting Number Guide:

  • Use a reliable casting number reference guide or online database to decode the number. You can find various resources on the internet or consult repair manuals specific to Chevrolet engines. These resources will provide information about the engine’s year, displacement, and main bearing cap configuration (2-bolt or 4-bolt).

4. Look for “010” or “020” Suffix:

  • In many cases, Chevrolet used engine blocks with “010” or “020” suffixes to indicate 4-bolt main blocks. For example, a casting number ending with “010” like “3970010” often indicates a 4-bolt main block.

5. Inspect the Main Bearing Caps:

  • If you have access to the engine, you can visually inspect the main bearing caps. A 4-bolt main engine will have four bolts securing each of the main bearing caps that hold the crankshaft in place. A 2-bolt main engine will have only two bolts per main bearing cap.

6. Seek Documentation:

  • If you have documentation, such as the original vehicle’s owner’s manual or a build sheet, it may provide information about the engine configuration.

7. Consult Experts or Forums:

  • If you’re still unsure, consider consulting with Chevrolet experts or enthusiasts on forums or social media groups dedicated to Chevy engines. They may be able to help you identify your engine based on photos or additional information you provide.

Identifying the main bearing cap configuration is essential if you’re planning to rebuild or modify your engine, as it can impact the engine’s strength and performance potential. Remember that Chevrolet has used various engine blocks over the years, so it’s crucial to check the casting number for accurate identification.

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