* Intake Manifold: The 351's intake manifold is significantly larger and taller than the 302's. This is the most obvious difference.
* Valve Covers: While not always definitive (some aftermarket valve covers exist), 351 valve covers are generally larger and wider than those on a 302.
* Distributor Location: Both are typically on the driver's side (looking from the front of the engine), but the 351's distributor is usually slightly further forward.
* Block Casting Number: This is the most reliable method. The block itself has a casting number stamped on it, usually on the side of the block near the front. These numbers are specific to the engine and year. You'll need a Ford engine casting number reference guide to decode it. This is readily available online.
* Spark Plug Arrangement: The 351 typically has a different spark plug arrangement (pattern) than the 302. This may be harder to see without removing the valve covers.
* Oil Filter Location: The oil filter location and design may be subtly different.
* Engine Size: The engine bay itself gives a visual clue; a 351 will physically appear larger and take up more space than a 302.
In short: While there are subtle differences, the intake manifold size and the block casting number are the most reliable ways to distinguish a 302 from a 351 Ford engine. Using an online Ford engine casting number database is crucial for accurate identification using the casting number method.
