LS firing order vs SBC

LS (Gen III/IV, including the 4.8/5.3/6.0 truck engines): 1-8-7-2-6-5-4-3 Small-block and big-block Chevy (1st/2nd gen): 1-8-4-3-6-5-7-2

Cylinder numbering didn't change: odd cylinders (1-3-5-7) are on the driver's side and even (2-4-6-8) on the passenger side on both engines. What changed is the order: GM swapped cylinders 4 and 7 and 2 and 3 in the sequence. Speedway credits the change with reducing internal harmonics for better high-rpm performance and durability.

Position	1	2	3	4	5	6	7	8
SBC / BBC	1	8	4	3	6	5	7	2
LS	1	8	7	2	6	5	4	3

Why it matters in a swap: LS engines use distributorless coil-near-plug ignition, so crossed plug wires between a distributor cap and the plugs aren't the usual problem. It still matters when you:

• run an LS carbureted — the coil-near-plug ignition then needs a standalone ignition controller (such as an MSD box) instead of the factory computer;
• diagnose a misfire by cylinder number — numbering matches the SBC, but the order doesn't, so SBC firing-order habits don't carry over.

Symptoms of an incorrect firing order include rough running and poor acceleration. Always confirm against the engine maker's spec.