Easy Visual Checks (If you can see the engine):
* Valve Covers: 351W valve covers are noticeably larger and taller than 302W valve covers. This is often the easiest way to tell them apart.
* Intake Manifold: While not always definitive (as aftermarket manifolds can be used), the factory intake manifold on a 351W is generally larger and bulkier than that of a 302W.
* Distributor: The distributor location is slightly different. While not a guaranteed method, it can be a clue.
* Engine Block Casting Numbers: These numbers, found on the side of the engine block, will definitively identify the engine. You'll need a casting number chart or a reliable online resource to decipher them.
More Involved Checks:
* Deck Height: The distance between the top of the engine block and the crankshaft centerline is different. A 351W has a taller deck height. This requires measurement and is not easily done without removing parts.
* Bore and Stroke: These measurements will be significantly different. A 351W has a larger bore and stroke than a 302W. Requires specialized tools to measure.
In short: The easiest and most reliable way to distinguish them is by comparing the valve covers and checking the engine block casting numbers. If you have access to neither, the intake manifold size can provide a reasonable guess, though not a guarantee. Other methods require more technical knowledge and tools.
