The Chevrolet 350 fires cylinders in the order 1-8-4-3-6-5-7-2
The firing order of a Chevrolet 350 engine is 1-8-4-3-6-5-7-2. This is the sequence in which the spark plugs ignite the fuel mixture in each cylinder, and it determines how you route the spark plug wires from the distributor cap to each cylinder. If the wires are connected in the wrong order, the engine will not run correctly — it may misfire, run rough, or not start at all.
The firing order is the same whether you have a small-block 350 (the most common version, produced from 1967 onward) or a big-block 350 (less common, produced in the 1960s). However, the physical layout of the cylinders on the engine block is different between the two, which affects how you physically route the wires even though the firing sequence stays the same.
Key Takeaways
- The Chevrolet 350 fires cylinders in the order 1-8-4-3-6-5-7-2, and this sequence applies to both small-block and big-block versions.
- Cylinder numbering on a small-block 350 runs 1-2-3-4 on the driver's side (left) and 5-6-7-8 on the passenger's side (right), with cylinder 1 at the front.
- Cylinder numbering on a big-block 350 runs 1-2-3-4 on the passenger's side (right) and 5-6-7-8 on the driver's side (left), which is the opposite of the small-block.
- The distributor cap has eight terminals arranged in a specific pattern, and the spark plug wires must follow the firing order when connected to those terminals.
- Tracing the firing order on a distributor cap requires knowing both the engine type and which direction the rotor spins inside the cap.
How cylinder numbering works on a small-block 350
On a small-block Chevrolet 350, cylinders are numbered 1 through 8 in a specific pattern. Cylinders 1, 2, 3, and 4 are on the driver's side of the engine (the left side when you face the front of the vehicle). Cylinders 5, 6, 7, and 8 are on the passenger's side (the right side). Cylinder 1 is always at the front of the engine, nearest the radiator.
This layout matters because when you look at the distributor cap — the round plastic component on top of the distributor — the terminals are arranged in a circle. The position of terminal 1 on that cap is fixed, and the other terminals are arranged around it in the order the rotor passes them. If you know where cylinder 1 is, you can trace the firing order around the cap and connect each wire to the correct terminal.
How cylinder numbering works on a big-block 350
On a big-block Chevrolet 350, the cylinder numbering is reversed compared to the small-block. Cylinders 1, 2, 3, and 4 are on the passenger's side (the right side when you face the front), and cylinders 5, 6, 7, and 8 are on the driver's side (the left side). Cylinder 1 is still at the front of the engine.
This reversal is one of the most common sources of confusion when working on a 350 engine. If you install spark plug wires using small-block cylinder positions on a big-block engine, or vice versa, the engine will not fire correctly. Before you begin, confirm which version of the 350 you have by checking your engine block or vehicle documentation.
Reading the distributor cap and rotor direction
The distributor cap has eight terminals arranged in a circle around its top. One terminal is marked with a notch, a line, or the number 1 — this is where the wire from cylinder 1 connects. The rotor inside the cap spins and passes each terminal in sequence, delivering spark to each cylinder in firing order.
Most Chevrolet 350 distributors have a rotor that spins clockwise when viewed from above. Starting at terminal 1, you move clockwise around the cap and place the wires in the order of the firing sequence: 1-8-4-3-6-5-7-2. However, some aftermarket or modified distributors may spin counterclockwise, which reverses the direction you trace around the cap. Check your distributor documentation or the rotor itself to confirm the direction.
Step-by-step wire routing for a small-block 350
To route spark plug wires on a small-block 350, start by locating terminal 1 on the distributor cap — it is usually marked and points toward the front of the engine. From terminal 1, move clockwise around the cap (assuming a standard clockwise-spinning rotor) and connect the wires in this order: terminal 1 to cylinder 1, terminal 2 to cylinder 8, terminal 3 to cylinder 4, terminal 4 to cylinder 3, terminal 5 to cylinder 6, terminal 6 to cylinder 5, terminal 7 to cylinder 7, terminal 8 to cylinder 2.
Remember that on a small-block, cylinders 1-4 are on the driver's side (left) and 5-8 are on the passenger's side (right). Trace each wire carefully from the cap to the correct spark plug, and do not rely on the old wires if they are still in place — they may have been installed incorrectly. If you are unsure about any connection, double-check against the firing order and cylinder positions before starting the engine.
Step-by-step wire routing for a big-block 350
To route spark plug wires on a big-block 350, locate terminal 1 on the distributor cap and move clockwise around the cap in the same firing order sequence: 1-8-4-3-6-5-7-2. The difference is in where those cylinders are physically located on the engine. On a big-block, cylinders 1-4 are on the passenger's side (right) and 5-8 are on the driver's side (left).
This reversal means that even though the firing order number sequence is identical to the small-block, the physical path of the wires across the engine is different. A wire that goes to the passenger's side on a small-block may go to the driver's side on a big-block, even though both are connecting to the same numbered cylinder in the firing sequence. Take time to verify each connection before running the engine.
Common mistakes when installing spark plug wires
The most frequent error is confusing small-block and big-block cylinder positions. If you have a big-block 350 and install wires using small-block positions, or vice versa, the engine will misfire or not start. Always confirm your engine type before beginning.
A second common mistake is assuming the old wires are correct. If the engine was running poorly before you removed the wires, the old routing may have been wrong. Always trace from the firing order and cylinder positions, not from what was already installed.
A third mistake is not accounting for rotor direction. Most Chevrolet 350 distributors spin clockwise, but some aftermarket units spin counterclockwise. If you trace the firing order in the wrong direction around the cap, every wire will be off by one or more positions. Check your distributor before you start.
Frequently Asked Questions
What happens if I connect the spark plug wires in the wrong order?
The engine will misfire, run rough, or not start at all. Misfiring means the cylinders are not firing in the correct sequence, so the power strokes do not occur in the right order and the engine cannot run smoothly. If the wires are severely out of order, the engine may not start even briefly.
How do I know if I have a small-block or big-block 350?
Small-block 350s are much more common and are narrower and lighter. Big-block 350s are taller and heavier. Check your vehicle's documentation, engine block casting numbers, or consult a repair manual for your specific year and model. If you are unsure, a mechanic can identify it in seconds.
Can I use the same spark plug wires on both a small-block and big-block 350?
The wires themselves are the same, but the routing is different because the cylinders are in different positions on the engine block. You can reuse the wires, but you must reconnect them to the correct cylinders based on whether you have a small-block or big-block.
Does the firing order change if I modify the distributor?
The firing order 1-8-4-3-6-5-7-2 does not change. However, if you install a distributor that spins counterclockwise instead of clockwise, you will trace the firing order in the opposite direction around the cap. Always verify rotor direction with your distributor documentation.
What if the terminal marked 1 on my distributor cap is not pointing toward the front of the engine?
The terminal marked 1 should point toward cylinder 1, which is at the front of the engine. If it does not, the distributor may be installed backward or the cap may be on upside down. Remove the cap, check the rotor position, and reinstall it so that terminal 1 points in the correct direction.