Choosing the Right Spark Plugs for Your 1987-1989 GMC R2500
Restore your classic GMC's power and smooth out its idle by selecting the correct new aftermarket spark plugs.
- Standard copper spark plugs from brands like NGK, Autolite, or Denso are the best choice for reliability and value in a stock R2500.
- Always check and set the spark plug gap to 0.035 inches before installation.
- Avoid expensive iridium plugs and gimmick-style plugs, as they provide no real benefit for this truck's ignition system.
- Consider replacing the spark plug wires, distributor cap, and rotor at the same time for a complete ignition tune-up.
Signs of Failing Spark Plugs
When your R2500's spark plugs are wearing out, you'll notice a few key symptoms. A rough idle, where the engine shakes or sounds uneven, is a common sign. You may also experience hesitation or sluggish acceleration, a drop in gas mileage, and difficulty starting the engine. In some cases, a misfiring spark plug can cause the engine to cough or sputter.
Choosing the Right Aftermarket Spark Plugs
For a 1987-1989 GMC R2500, you don't need fancy or expensive plugs to get great performance. The original ignition systems on these trucks were designed for standard copper core spark plugs, and they still work exceptionally well. Aftermarket brands offer excellent quality that often meets or exceeds the original AC Delco specifications.
Brand Quality Tiers
| Tier | Brands | Description |
|---|---|---|
| Standard Replacement (Good) | Autolite, Champion | These brands offer reliable, budget-friendly copper plugs that are a direct replacement for the original parts. They perform well but may have a shorter lifespan, requiring changes around every 20,000-30,000 miles. |
| Premium Replacement (Better) | NGK, Denso, Bosch | NGK and Denso are highly regarded for their quality and consistency, often considered an upgrade over standard plugs. Their V-Power or standard copper designs are excellent for the R2500's engines. Bosch also provides quality options that meet OEM requirements. |
| Performance (Specialty Use) | Accel, MSD | These brands are geared towards modified or high-performance engines. Accel offers "shorty" plugs that can help with clearance issues if you have aftermarket exhaust headers. For a stock or lightly modified R2500, these are generally not necessary. Some owners have reported issues with Accel plugs being bad out of the box. |
Avoid Gimmick Plugs
For this generation of GMC truck, it's best to avoid plugs with multiple ground electrodes or exotic designs like the E3. The simple, time-tested single-electrode copper plug provides the most reliable performance for the stock ignition system. Many owners who try gimmick plugs report rough running and switch back to standard designs.
Known Issues, Recalls, and TSBs
There are no active recalls or Technical Service Bulletins (TSBs) specifically related to spark plug failure on the 1987-1989 GMC R2500. Any issues you encounter will almost certainly be due to normal wear and tear. A TSB from the era does mention "Miss, Hesitation, or Roughness," which can be caused by worn plugs, but it is not a component-specific bulletin.
Pro Tip: Check the Gap!
Always check the spark plug gap before installation, even if the box says they are "pre-gapped." The correct gap for most gasoline V8 engines (like the 5.0L, 5.7L, and 7.4L) in this truck is 0.035 inches. An incorrect gap can lead to poor performance and misfires. Using a feeler gauge or gapping tool is essential for this job.
Frequently Asked Questions (FAQ)
How often should I change the spark plugs?
If you use standard copper plugs, a good replacement interval is every 20,000 to 30,000 miles. This ensures your engine maintains peak performance and fuel efficiency. While more expensive iridium or platinum plugs can last longer, the simple and affordable copper plugs, changed regularly, are perfect for these trucks.
Do I need special tools to change the spark plugs?
You will need a standard ratchet, a spark plug socket (usually 5/8"), and a socket extension. A spark plug wire puller can be helpful to avoid damaging the wires. A torque wrench is recommended for proper tightening, and a gapping tool is a must-have to set the gap correctly.
Should I use anti-seize on the threads?
This is a topic of debate. Some plug manufacturers, like NGK, advise against it because their plugs have a special plating that prevents seizing. If you do use anti-seize, use only a very small amount on the threads and reduce the torque setting by about 10-15% to avoid over-tightening.
What about spark plug wires?
When you change your plugs, it's a great time to inspect the spark plug wires, distributor cap, and rotor. These components wear out over time and are critical to the ignition system. If the wires are original or look cracked and brittle, replacing them with a quality aftermarket set is a smart move.
Technical Specifications
OEM Part Numbers: ACDelco CR43TS ACDelco R44TS ACDelco R45TS
Spark Plug Gap: 0.035 inches (for gasoline engines). Socket Size: 5/8 inch.
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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.
- GMC R2500: