Fargo D200 Panel Delivery Spark Plug Guide: 1966-1967
Get the right spark plugs for your classic Fargo's Slant-6 or V8 engine and keep it running smoothly.
- You must identify your engine (Slant-6 or V8) before buying plugs, as they are not interchangeable.
- Stick to standard copper-core spark plugs from Champion or Autolite; avoid modern platinum or iridium plugs.
- If you have a Slant-6, you must remove the crush washer from the new spark plugs before installation.
- Always check and set the spark plug gap to 0.035 inches before installing.
Engine Comes First: Slant-6 vs. V8
Before buying spark plugs, you must know which engine is in your Fargo D200. During this era, these trucks came with two main engine types: the 225 cubic inch "Slant-6" and V8 options, most commonly the 318 cubic inch "Poly" V8. These engines use different spark plugs. Installing the wrong plug can cause poor performance or even engine damage. The Slant-6 is easy to identify as it is visibly tilted to one side in the engine bay.
Symptoms of Failing Spark Plugs
The simple ignition systems in these classic trucks are very sensitive to spark plug condition. If your plugs are worn, fouled, or have an incorrect gap, you'll likely notice it. Common symptoms include:
- Hard Starting: The engine cranks for a long time before it finally fires up, especially when cold.
- Rough Idle: Your truck shakes or sputters when it's stopped, like at a traffic light.
- Engine Misfires: You can feel a hesitation, stumble, or jerking from the engine, particularly when you accelerate.
- Reduced Power: The truck feels sluggish and doesn't accelerate as it should.
- Poor Fuel Economy: Worn plugs lead to inefficient combustion, meaning you'll be making more trips to the gas station.
A Note on Modern Plugs
Avoid using platinum or iridium spark plugs in your Fargo's original engine. The ignition systems in these trucks were engineered for standard copper-core plugs. While modern plugs won't cause harm, they offer no performance benefit and can sometimes run worse than the inexpensive copper plugs the engine was designed for. Stick with what works.
Choosing the Right Aftermarket Spark Plug
For a vintage truck, the choice is straightforward. You'll want a standard copper-core spark plug from a reputable brand.
- Champion: Champion was often the original equipment (OE) brand for Mopar vehicles in the 1960s. Many owners choose Champion to maintain an original appearance and performance. They are a reliable, cost-effective choice that works well in these engines.
- Autolite: Autolite is a very popular and high-quality aftermarket alternative. Some classic truck owners prefer them over Champion, citing good performance and durability. You can't go wrong with either brand.
Special Instructions for the Slant-6 Engine
If you have the 225 Slant-6 engine, the spark plugs install inside tubes that seal against the cylinder head. When installing new plugs, it is critical that you remove the small metal crush washer from the new spark plug before installation. The plug is designed to seal against the bottom of the tube. Leaving the washer on will position the plug incorrectly in the combustion chamber, leading to poor performance.
Cost of New Aftermarket Spark Plugs (1966-1967 Fargo D200)
| Item | Estimated Cost |
|---|---|
| New Aftermarket Spark Plug (per plug) | $3.50 - $9.31 |
| Shop Labor (for all plugs) | $75 - $150 |
Note: Your truck will need six (Slant-6) or eight (V8) spark plugs. Costs are estimates and may vary based on location and supplier.
Frequently Asked Questions
How often should I change the spark plugs on my Fargo D200?
For a classic truck using standard copper plugs, a good interval is every 10,000 to 15,000 miles, or every two years. Given their low cost, changing them regularly is cheap insurance for maintaining engine health and reliability.
What is the correct spark plug gap?
For most standard ignition systems on these trucks, the correct spark plug gap is 0.035 inches. However, it's always best to verify. Even if a plug is advertised as "pre-gapped," you should always check and adjust the gap with a proper tool before installation, as they can be easily knocked out of spec during shipping.
Are there any recalls for my truck's spark plugs?
No. A search of the National Highway Traffic Safety Administration (NHTSA) database shows no recalls or technical service bulletins (TSBs) for spark plugs on the 1966-1967 Fargo or Dodge D200. Issues with this part are related to normal wear and tear.
What tools do I need to change my spark plugs?
The job is simple and requires only basic tools. You will need a ratchet, a spark plug socket (this has a rubber insert to protect the plug's ceramic), a socket extension, and a spark plug gapping tool. For V8 engines, some plugs may be harder to reach, but the job is still very manageable.
Technical Specifications
Engine-specific. Common gap setting is 0.035 inches. Use standard copper-core resistor plugs. V8 and Slant-6 engines require different plugs.
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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.