Most Chevy small block and big block V-8 engines use the firing order 1-8-4-3-6-5-7-2. The LS family of V-8 engines has a 1-8-7-2-6-5-4-3 firing order, according to Reference.com. Firing order designates the way spark plugs fire and internal combustion supplies power from the engine.
Correct placement of spark plug wires on the distributor results in the correct firing order with gasoline engines using mechanical points. In engines using direct ignition, the engine control unit, a vehicle's on-board computer, ensures the plugs fire in the correct order. Most manufacturers cast the firing order on the cylinder head, valve cover or intake manifold, especially on vehicles with distributors.
Attaching plug wires in the wrong firing order causes rough idle and backfiring. In some cases, the vehicle fails to start.
With GM V-8 engines, the number one cylinder is located at the front of the engine on the driver's side of the vehicle. GM does not use V-8s in front-wheel drive vehicles with transverse-mounted engines. On Chevy engines, the odd-numbered cylinders are on the driver's left and the even are on his right.
Ford numbers their engine cylinders with 1-4 on the driver's left and 5-8 on the right. While their firing pattern is 1-3-7-2-6-5-4-8, a careful comparison shows the corresponding pistons fire in the same order as the Chevy big- and small-block engines.