Visual Inspection:
* Casting Numbers: This is the most reliable method. The engine block will have casting numbers stamped into various locations, most prominently on the block itself near the passenger side cylinder head. These numbers will indicate the year and specific casting of the block. You'll need a reference guide (many are available online) to cross-reference these numbers to confirm it's a 400. There are various casting numbers used over the years the 400 was produced.
* Valve Covers: While not definitive, the valve covers often have "Chevrolet" cast into them, and some aftermarket valve covers are specific to the 400's size. However, valve covers can be easily changed, so this is not a reliable identifier on its own.
* Intake Manifold: While again not definitive, some intake manifolds are specific to the 400.
* Size and Dimensions: The 400 is physically larger than the 350 small block. Measuring the deck height or comparing its overall size to known 350 blocks might help if you have something to compare it to, but it's not precise enough on its own.
* Distributors: While not exclusive to the 400, the distributor's location and style may give you a clue.
Indirect Methods:
* Vehicle Documentation: If you have the original paperwork for the vehicle, it should specify the engine type.
* Service Records: Service records may list the engine displacement.
Important Considerations:
* Modifications: The engine might have been modified, and some external parts may have been changed, making visual identification more difficult.
* Accuracy: Relying on visual cues alone is not always reliable. The casting numbers are the key to accurate identification.
In short: Find the casting numbers on the block. Use a reliable reference guide (easily found online) to decipher them and determine if it's indeed a Chevy 400. This is the only truly reliable method.
