Essential Spark Plug Guide for the 1987 GMC R1500
Get your classic GMC running right by choosing the best spark plugs for its V6 or V8 engine.
- Stick with standard copper-core spark plugs for the best performance with the original ignition system.
- ACDelco and NGK are the most recommended brands for reliability and proper function in your R1500.
- Always verify the spark plug gap is set to 0.035 inches before you install them.
- Avoid expensive platinum and iridium plugs, as they do not offer a benefit for this engine and may cause issues.
Signs of Failing Spark Plugs
Worn-out spark plugs can cause noticeable issues in your truck. Because these classic GMCs have simpler engine systems, they are very sensitive to spark plug condition. Look for these common symptoms:
- Rough Idle: The engine may shake or run unevenly when you're stopped at a light.
- Engine Misfires: You might feel a hesitation, stumble, or bucking during acceleration as a cylinder fails to fire correctly.
- Poor Acceleration: The truck may feel sluggish or down on power when you press the gas pedal.
- Reduced Fuel Economy: If you find yourself filling up the tank more often, worn plugs could be wasting fuel by not burning it completely.
- Hard Starting: A weak spark from old plugs can make the engine difficult to start, especially when cold.
A Note on Check Engine Lights
Your 1987 R1500 is a pre-OBD-II vehicle. This means it does not have the modern diagnostic system that provides specific codes like "P0301" for a misfire in cylinder 1. While the "Check Engine" light might come on for a persistent issue, you'll need to rely on feeling the symptoms to diagnose failing plugs.
Choosing the Right Aftermarket Spark Plug
For your 1987 R1500, the original factory technology is the most important factor. Newer, more expensive plugs are not always better for this truck.
Material: Copper is King
Your truck's High Energy Ignition (HEI) system was designed to work with standard copper-core spark plugs. While modern plugs made of platinum or iridium boast a longer lifespan, they often require higher voltage to create a strong spark. On this vintage ignition system, they can actually provide a weaker spark, leading to rough running or a less efficient engine. For the best performance and reliability, stick with copper plugs.
Aftermarket Brand Tiers for Your R1500
Based on owner feedback and mechanic recommendations, here’s how the available brands stack up for your specific truck:
| Tier | Brands | Assessment |
|---|---|---|
| OEM-Style / Highly Recommended | ACDelco, NGK | ACDelco is the original equipment brand and a guaranteed fit for performance and reliability. NGK is a top-tier aftermarket choice, widely praised by owners of classic GM trucks for its quality and consistent performance. |
| Reliable Alternatives | Autolite, Denso | Standard copper plugs from these brands are a solid choice. Autolite has a long-standing reputation for reliability in domestic vehicles. Denso is another quality manufacturer. |
| Economy Choice | Champion | While Champion is a well-known name, some users report occasional issues like misfires compared to NGK or ACDelco in similar applications. They are a functional budget option. |
| Performance / Specialty | MSD, Accel | These brands are geared towards modified, high-performance engines with upgraded ignition systems. For a stock or lightly modified R1500, they are unnecessary and more costly. |
Check The Gap!
Always check the spark plug gap before installation using a gap tool. The correct gap for most 1987 R1500 V8 engines is 0.035 inches. Do not assume the plugs are gapped correctly out of the box.
Frequently Asked Questions (FAQ)
How often should I change the spark plugs on my 1987 R1500?
For standard copper plugs, a good interval is every 20,000 to 30,000 miles. This is a simple and inexpensive maintenance task that keeps your classic truck running at its best.
Should I use anti-seize on the spark plug 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 your tightening torque by about 10-15% to avoid over-tightening.
Are platinum or iridium plugs a worthwhile upgrade?
No. For this specific vehicle and its ignition system, platinum and iridium plugs are not a recommended upgrade. They are more expensive and may negatively affect performance. Stick with the copper plugs the engine was designed for.
Do I need special tools to change my spark plugs?
You will need a ratchet, a spark plug socket (typically 5/8-inch for these plugs), and a socket extension. A gap tool is also essential to ensure the plugs are gapped correctly before installation.
Technical Specifications
OEM Part Numbers: ACDelco R45TS ACDelco CR43TS General Motors 5613957
Seat Type: Tapered Hex Size: 5/8 inch Recommended Gap: 0.035 inches Core Material: Copper
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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 R1500: