Choosing the Right Spark Plugs for Your 1966-1972 Fargo W100 Pickup
Get the right spark and keep your classic Fargo running strong with the correct new plugs.
- Stick with standard copper-core spark plugs from Champion or Autolite; they were designed for your truck's ignition system.
- You must know if you have the Slant-6 or V8 engine to get the correct plugs.
- Always check and set the spark plug gap to your engine's specification (usually 0.035 inches) before installation.
- To avoid mistakes, change one spark plug at a time to ensure the ignition wires are not mixed up.
Is it Time for New Spark Plugs?
Your 1966-1972 Fargo W100 doesn't have a check engine light. You need to pay attention to how the truck sounds and feels. Worn-out spark plugs can cause several problems because the simple ignition systems are very sensitive to plug condition. If you notice a rough idle, engine misfires, poor acceleration, or bad gas mileage, it might be time for new plugs.
Choosing the Right Aftermarket Spark Plugs
For a classic truck like the Fargo W100, sticking to the basics is usually best. The original ignition systems were designed for standard copper-core spark plugs. Using expensive plugs with rare materials like platinum or iridium will not improve performance and can sometimes make the engine run worse. Stick with what works.
It is important to know which engine your truck has. The two most common engines are the 225 cubic inch "Slant-6" and the 318 cubic inch V8. Both have different spark plug requirements.
| Tier | Brands | Quality & Notes |
|---|---|---|
| Good (Recommended) | Champion, Autolite | Champion was the original equipment manufacturer (OEM) for many Chrysler, Dodge, and Fargo vehicles of this era. They are a reliable choice. Autolite is another excellent aftermarket brand that makes copper-core plugs well-suited for these vintage engines. Both offer dependable performance at a good price. |
| Not Recommended | E3, Bosch Multi-Electrode | Plugs with special designs, like E3 or multi-electrode plugs (Bosch +2/+4), are generally not recommended for these older engines. The ignition systems were not designed for them, and they can cause performance issues. |
Known Issues, Recalls, or TSBs
There are no recalls or Technical Service Bulletins (TSBs) from the National Highway Traffic Safety Administration (NHTSA) for spark plugs on the 1966-1972 Fargo W100. Any problems you might have are likely due to normal wear, old parts, or incorrect installation.
Cost for New Aftermarket Spark Plugs (1966-1972 Fargo W100)
| Part Type | Price Range (per plug) |
|---|---|
| New Aftermarket Spark Plug | $3.50 - $9.31 |
Pro Tip: Always check the spark plug gap before you install them. A common gap for these engines is 0.035 inches, but you should check a service manual for your specific engine. An inexpensive gapping tool can save you from performance problems.
🎬 Follow this DIY guide for more spark plug installation tips.Frequently Asked Questions
How often should I change the spark plugs?
For standard copper plugs in a classic truck, a good rule is to inspect them every 10,000 miles and replace them every 20,000 to 30,000 miles, or whenever you notice performance issues.
Should I use anti-seize on the new spark plugs?
This is a topic of debate. Some mechanics recommend a very small amount of nickel anti-seize on the threads to prevent them from getting stuck in the cylinder head. However, many modern plug manufacturers advise against it as it can lead to over-tightening. If you do use it, use it sparingly and reduce the tightening torque slightly.
What is the most common mistake when changing spark plugs?
The most common mistakes are mixing up the spark plug wires, over-tightening the plugs, and not checking the gap. To avoid mixing up wires, change one plug at a time. To avoid over-tightening, thread the new plug in by hand first, then use a wrench for the final tightening (about a quarter-turn once the gasket seats 🎬 Watch this step-by-step tutorial on how to replace spark plugs.).
Does it matter which brand I choose between Autolite and Champion?
For these trucks, both are excellent choices. Many Mopar purists prefer Champion because they were the original plug. However, many owners have had great success with Autolite as well. The most important thing is to get the correct copper-core plug for your specific engine and gap it properly.
Helpful Videos
Technical Specifications
OEM Part Numbers: N9YC N12YC 3420751
Engine Type: 225 Slant-6 or 318 V8. Plug Type: Standard Copper Core. Recommended Gap: 0.035 inches (verify with service manual). Seat Type: Gasket.
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.