Spark Plug Replacement and Upgrade Guide for 1977-1988 Dodge D150
Get the right spark plugs for your Slant-6 or V8 and bring back that classic Mopar power and reliability.
- For stock 1977-1988 D150s, standard copper-core spark plugs like Champion RN12YC or NGK V-Power are the most recommended and cost-effective choice.
- Always check and set the spark plug gap to 0.035 inches before installation, as plugs can be handled roughly during shipping.
- Symptoms like rough idle, misfiring, and hard starting point to worn plugs, but also check the distributor cap, rotor, and wires.
- There are no specific recalls or TSBs for spark plugs on these trucks; failures are due to normal wear.
Signs of Failing Spark Plugs in Your D150
The spark plugs in your 1977-1988 D150 are wear items. As they age, the electrodes wear down, and deposits can build up, leading to a weak or inconsistent spark. If you're experiencing any of these issues, your plugs might be telling you it's time for a change.
- Rough Idling: An uneven or shaky idle is a classic sign of a worn spark plug causing a cylinder to misfire.
- Hard Starting: If your truck cranks for a long time before the engine catches, weak spark plugs could be the culprit.
- Engine Misfires: You might feel a hesitation or stumble, especially under acceleration, as a cylinder fails to fire correctly.
- Reduced Fuel Economy: An incomplete burn of the air-fuel mixture means you're not getting the most out of every gallon of gas.
- Loss of Power: If your D150 feels sluggish or struggles to get up to speed, worn plugs can be a contributing factor.
"No Spark" Isn't Always the Plugs
If your truck won't start and you have no spark at all, the issue could be another part of the ignition system. Owners often report issues with the ignition module, ballast resistor, or pickup coil in the distributor 🎬 Watch: Troubleshooting no spark issues on Mopar electronic ignitions on these trucks. While you have the plugs out, it's a good time to inspect your distributor cap, rotor, and spark plug wires as well.
Choosing the Right Aftermarket Spark Plugs
For the engines used in this generation of Dodge trucks—like the 225 Slant-6, 318 V8, and 360 V8—the original design called for simple, copper-core spark plugs. While modern options like platinum and iridium exist, many owners find that sticking with the basics is the most reliable and cost-effective choice.
Tier 1: Standard Copper (OEM-Style)
These are the workhorses. They are what your truck likely came with from the factory. They offer excellent performance for these engines at a very low cost. The trade-off is a shorter lifespan, typically needing replacement every 15,000 to 30,000 miles.
- Champion Copper Plus: Often considered the original equipment plug. The Champion RN12YC is a very common recommendation for the 318 and 360 V8 engines.
- NGK V-Power: A very popular and high-quality alternative. Many Mopar enthusiasts prefer NGK for their consistent manufacturing quality.
- Autolite Copper Core: Another reliable and affordable option that works well in these engines.
Tier 2: Platinum & Iridium Plugs
These plugs feature electrodes made from more durable, precious metals. They are designed to last much longer, sometimes up to 100,000 miles. While they are available for the D150, many owners report that these simple, carbureted (or early fuel-injected) engines don't see a significant performance benefit to justify the higher cost. Some even report that the engines run better on standard copper plugs.
- Bosch Platinum
- ACDelco Platinum/Iridium
- Denso Iridium Power
- NGK Iridium IX
Pro Tip: Check the Gap!
No matter which brand or type of spark plug you buy, always check the gap before installation. The recommended gap for most stock D150 engines is 0.035 inches. Plugs can be dropped during shipping, causing the gap to close. Use a feeler gauge or gapping tool to ensure it's set correctly for your engine.
🎬 See this walkthrough for changing plugs on a classic RamCost of New Aftermarket Spark Plugs (1977-1988 Dodge D150)
| Tier | Price Range (per plug) | Total for 6-Cyl | Total for V8 |
|---|---|---|---|
| Standard Copper (Champion, NGK, Autolite) | $3.00 - $5.00 | $18 - $30 | $24 - $40 |
| Platinum / Iridium (Bosch, Denso, NGK) | $6.00 - $20.00+ | $36 - $120+ | $48 - $160+ |
Note: Prices are estimates and can vary based on brand and retailer. These prices reflect the new aftermarket parts available in our inventory.
Frequently Asked Questions (FAQ)
Do I need expensive iridium or platinum plugs for my D150?
Generally, no. The ignition systems on these trucks were designed for standard copper-core spark plugs. While premium plugs will work, they don't typically offer a noticeable performance gain and are not necessary for reliability. Sticking with a quality copper plug from a brand like Champion or NGK is a proven, cost-effective strategy.
What is the correct spark plug gap for my Dodge D150?
For most stock 1977-1988 D150 engines (Slant-6 and V8s), the standard spark plug gap is 0.035 inches. If you have a modified ignition system (like an MSD box), you might run a wider gap, but for a stock truck, 0.035" is the correct setting. Always verify the gap on new plugs before installing them.
Should I use anti-seize on the spark plug threads?
This is a topic of debate. Some mechanics always apply a small amount of copper anti-seize to the threads to prevent the plugs from getting stuck in the cast iron cylinder heads. However, some spark plug manufacturers, like NGK, apply a special plating to their plugs that serves the same purpose and advise against using anti-seize, as it can affect torque readings and grounding. If you do use it, apply only a very thin layer to the threads, avoiding the electrode and ground strap completely.
🎬 Watch: Step-by-step spark plug and wire replacement for the 318 V8How often should I change the spark plugs on my D150?
If you are using standard copper-core plugs, a good interval is every 15,000 to 30,000 miles, or every 2-3 years. This ensures the engine is always running with a fresh, properly gapped plug for optimal performance and fuel economy. If you opt for platinum or iridium plugs, you can go much longer, but given the low cost of copper plugs, frequent changes are easy preventative maintenance.
Are there any recalls for spark plugs on the 1977-1988 D150?
No, there are no official NHTSA recalls or widespread Technical Service Bulletins (TSBs) specifically for spark plug failure on the 1977-1988 Dodge D150. Any issues are typically related to normal wear and tear or other ignition system components.
Helpful Videos
![No Spark Troubleshooting [Mopar Electronic Ignition with Ballast Resistor]](https://img.youtube.com/vi/RiC8OaSXMs8/mqdefault.jpg)
Technical Specifications
OEM Part Numbers: RN12YC
For most V8 applications, the key specifications are a 14mm thread, 13/16" hex size, and a gasket seat. The most critical specification is the spark gap, which should be set to 0.035" for stock engines.
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.
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Signs of Failing Spark Plugs in Your D150
- "No Spark" Isn't Always the Plugs
- Choosing the Right Aftermarket Spark Plugs
- Tier 1: Standard Copper (OEM-Style)
- Tier 2: Platinum & Iridium Plugs
- Pro Tip: Check the Gap!
- Cost of New Aftermarket Spark Plugs (1977-1988 Dodge D150)
- Frequently Asked Questions (FAQ)
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