An inline-six engine *cannot* have a 1-4-2-5-3-6 firing order. The firing order must be designed to balance the engine's vibrations and ensure even crankshaft loading. A 1-4-2-5-3-6 order would create significant imbalance and uneven torque pulses. Typical inline-six firing orders aim for a roughly 120-degree interval between power strokes.
Common inline-six firing orders include 1-5-3-6-2-4 and its mirror image.
