The firing order for a 350 small block Chevrolet is 1-8-4-3-6-5-7-2

This sequence tells you the order in which each cylinder fires — that is, when the spark plug ignites the fuel mixture in that cylinder. The cylinders are numbered 1 through 8, and they fire in that specific pattern as the crankshaft rotates. If you're rebuilding an engine, installing new spark plug wires, or troubleshooting a misfire, you need to know this order to connect the wires correctly to the distributor cap.

The 350 small block is one of the most common engines in American vehicles, so this firing order appears in countless repair manuals and online resources. However, the actual wires on your engine may be arranged differently depending on the year, model, and whether the engine has been modified. The firing order itself never changes — but how you route the wires to match it does.

Key Takeaways

  • The firing order 1-8-4-3-6-5-7-2 is the sequence in which cylinders ignite, and it is the same for all 350 small block engines.
  • Cylinder numbering on a 350 small block runs 1-2-3-4 on the driver's side and 5-6-7-8 on the passenger side, with cylinder 1 at the front of the engine.
  • The distributor cap has eight terminals arranged in a specific pattern, and you must route spark plug wires from the cap to each cylinder in the firing order sequence.
  • If spark plug wires are installed in the wrong order, the engine will misfire, run rough, or not start at all.
  • Tracing the existing wire routing before disconnecting anything helps you avoid mistakes when reinstalling or replacing wires.

How cylinder numbering works on a 350 small block

The eight cylinders are divided into two banks: the driver's side (left) and the passenger's side (right) when you face the front of the engine. On the driver's side, cylinders are numbered 1, 2, 3, and 4 from front to back. On the passenger's side, they are numbered 5, 6, 7, and 8, also from front to back. Cylinder 1 is always the front-most cylinder on the driver's side.

This numbering scheme is standard across Chevrolet 350 engines, but you should verify it on your specific engine before you start work. The easiest way is to look at the engine block itself — many blocks have the numbers cast into the metal near the cylinder head. If the numbers are not visible, consult the service manual for your vehicle year and model, which will include a diagram showing the exact layout.

Understanding the distributor cap and wire routing

The distributor cap sits on top of the distributor and has eight terminals arranged around its perimeter. Each terminal connects to one spark plug wire, and each wire runs to one cylinder. The distributor's rotor spins inside the cap and makes contact with each terminal in sequence, sending the spark signal to that cylinder at exactly the right moment.

The terminal positions on the cap are not random — they follow a specific pattern that matches the firing order. When you look at the cap from above, you will see a notch or mark that indicates the number 1 terminal position. From there, the remaining terminals are numbered or positioned so that the rotor contacts them in the firing order sequence: 1-8-4-3-6-5-7-2. If you install a wire in the wrong terminal, that cylinder will fire at the wrong time, causing a misfire.

Steps to route spark plug wires correctly

Step 1: Locate the number 1 terminal on the distributor cap. This is usually marked with a raised line, a notch, or the number 1 printed on the cap itself. If you cannot find it, consult your service manual or look for a diagram on the underside of the cap.

Step 2: Identify which spark plug wire currently connects to the number 1 terminal. Follow that wire to the cylinder it serves — this should be cylinder 1 (front of the driver's side). If it does not, the wires are already out of order, and you will need to correct them.

Step 3: Trace each existing wire from the cap to its cylinder before disconnecting anything. Write down or photograph which terminal each wire comes from and which cylinder it goes to. This creates a reference in case you need to check your work later.

Step 4: Disconnect one wire at a time and reconnect it to the correct terminal. Working one wire at a time reduces confusion. Use the firing order 1-8-4-3-6-5-7-2 and the terminal positions on your cap to determine where each wire should go.

Step 5: Double-check your work by tracing each wire from cap to cylinder. The wire from terminal 1 should go to cylinder 1, the wire from terminal 8 should go to cylinder 8, and so on through the entire firing order sequence.

What happens if the firing order is wrong

An incorrect firing order causes the engine to misfire because cylinders ignite out of sequence. The engine may run very rough, hesitate during acceleration, backfire through the exhaust, or fail to start at all. The severity depends on how many wires are in the wrong position — a single wire out of place may cause a subtle misfire, while multiple wires reversed can prevent the engine from running entirely.

If you have just installed new spark plug wires or reconnected the distributor cap and the engine is not running smoothly, the first thing to check is the wire routing. Verify that each wire connects to the correct terminal on the cap and that the wire runs to the correct cylinder. Many engine problems blamed on fuel or ignition systems are actually caused by wires installed in the wrong order.

Finding the firing order for your specific engine

The 350 small block firing order is consistent across all years and models, but you should always verify it against your vehicle's service manual before you begin work. Manuals are available from the manufacturer, through online repair databases, or in printed form at auto parts stores. The manual will include a diagram showing cylinder numbering, distributor cap terminal positions, and the correct wire routing for your specific year and engine configuration.

If you cannot locate a manual, many online forums and technical websites dedicated to Chevrolet engines maintain firing order diagrams and wire routing charts. However, always cross-reference information from multiple sources to may support accuracy. A few minutes spent verifying the correct order saves hours of troubleshooting if something goes wrong.

Frequently Asked Questions

Does the firing order change if the engine has been modified?

No. The firing order 1-8-4-3-6-5-7-2 is determined by the engine's internal design and never changes, regardless of modifications. However, modifications like a different distributor or ignition system may change how you route the wires or which terminals you use. Always consult documentation for any aftermarket parts you install.

What if I cannot find the number 1 terminal on my distributor cap?

Look for a raised line, notch, or printed number on the cap itself. If the cap is worn or unmarked, check the underside for any indication. Your service manual will show the exact location. As a last resort, you can remove the cap and look inside — the rotor should point toward the number 1 terminal when the engine is set to top dead center on cylinder 1.

Can I mix up the firing order if I only replace one spark plug wire?

Only if you disconnect the wire from the wrong terminal or route it to the wrong cylinder. If you are replacing a single wire, trace it from the old cap terminal to the old cylinder, then install the new wire in exactly the same path. Replacing one wire should not change the overall firing order unless you make a mistake during installation.

How do I know if my wires are in the wrong order?

The engine will misfire, run rough, hesitate, or not start. You may also see a check engine light or smell unburned fuel. The quickest way to verify is to trace each wire from the distributor cap to its cylinder and compare the routing against the firing order 1-8-4-3-6-5-7-2. If any wire is out of sequence, that is your problem.