How can i tell the difference between a Chevrolet 350Ci and 305Ci 1986 in my C10 pickup?

The easiest way to definitively tell the difference between a 1986 Chevrolet 350ci (5.7L) and a 305ci (5.0L) small-block engine in your C10 is to check the engine block casting number. This number is usually found on the front passenger side of the block, near the cylinder head. It's often a raised number, but might be stamped. You might need a flashlight and a wire brush to clean it off for better visibility.

A quick visual inspection can offer clues, but isn't definitive:

* Size: The 350 generally appears slightly larger and taller than the 305, but this isn't always reliable. Differences are subtle and depend on accessories.

* Intake Manifold: The intake manifold *might* be different, but many aftermarket and even some stock manifolds will fit both.

* Valve Covers: Again, valve covers aren't a reliable indicator. Many different valve covers can be used on both engines.

To be certain:

1. Find the engine block casting number. This is the most accurate method. Use a casting number lookup online (many websites exist for this; search "Chevrolet small block casting number lookup"). Input the number, and it will tell you the engine displacement.

2. Check the vehicle identification number (VIN) decoder. While the VIN *might* list the engine, it's not always completely reliable for the exact engine type. It's a good secondary check but not a primary identification method.

Don't rely on visual cues alone. The engine casting number is your definitive answer.