Choosing the Right Spark Plugs for Your 1979-1987 GMC G2500
Get the right spark plugs for your classic G-series van to ensure it runs smoothly and reliably.
- For stock engines, use standard copper-core spark plugs from brands like ACDelco (R45TS) or NGK.
- Avoid expensive iridium or platinum plugs, as they offer no performance benefit for these older ignition systems.
- Always check and set the spark plug gap before installation, typically to .035-.045 inches for HEI systems.
- Accessing all the plugs can be difficult; some may be easier to reach from the wheel wells or underneath the van.
Signs of Failing Spark Plugs
The simple, durable engines in 1979-1987 GMC G2500 vans are known for their longevity, but they depend on healthy spark plugs to run properly. When plugs wear out, you'll notice the difference. Look for these common symptoms:
- Rough Idle: Your van may shake or sputter when it's stopped.
- Engine Misfires: You might feel a hesitation or stumble from the engine, especially when accelerating or hauling a heavy load.
- Poor Acceleration: The van feels sluggish and lacks the power it once had.
- Reduced Fuel Economy: If you're making more frequent stops at the gas station, failing plugs could be wasting fuel.
- Difficulty Starting: A worn plug makes it harder for the engine to fire up, particularly on cold mornings.
Choosing the Right Aftermarket Spark Plug
For these classic vans, newer and more expensive doesn't always mean better. The original ignition systems were designed for traditional, standard-style spark plugs.
Aftermarket Brand Tiers
| Tier | Brands | Quality Assessment |
|---|---|---|
| OEM & Premium Aftermarket | ACDelco, NGK | ACDelco was the original equipment manufacturer for GM and their standard copper plugs, like the R45TS, are considered the go-to choice for originality and reliability. NGK is a highly respected brand known for excellent quality and is a fantastic alternative if ACDelco is unavailable. Both are consistently recommended in owner forums. |
| Quality Aftermarket | Denso, Champion, Autolite, Bosch | These brands have been making spark plugs for decades and offer reliable performance for daily driving. Denso is a strong competitor to NGK. Champion plugs are a traditional choice for these engines. While many owners use Autolite and Bosch without problems, some forum discussions mention occasional quality control concerns with these brands in older applications. |
| Economy | Skyward | Economy brands can be a budget-friendly option. However, for a critical and inexpensive part like a spark plug, sticking with a proven brand is recommended to ensure reliability and avoid potential running issues. |
Pro Tip: Stick with Copper Plugs
The engines in the 1979-1987 G2500 were designed to use standard copper-core spark plugs. Expensive platinum and iridium plugs, designed for modern high-energy ignition systems, often provide no benefit in these older engines and can sometimes perform worse. Copper plugs are affordable and provide the strong spark these engines need, though they should be changed more frequently, typically every 20,000 to 30,000 miles.
Known Issues & Recalls
A search of the National Highway Traffic Safety Administration (NHTSA) database shows no specific recalls or technical service bulletins (TSBs) for spark plugs on the 1979-1987 GMC G2500. This is common for vehicles of this age. While no specific bulletins exist, owners on forums sometimes report ignition module failures, which can be related to the overall health of the ignition system, including plugs and wires. Keeping up with spark plug changes is a good preventative measure.
Installation Tips
Changing the spark plugs on a G2500 van can be challenging due to tight access, especially from inside the cabin after removing the engine cover ('doghouse'). Some plugs may be easier to reach from underneath or through the wheel wells. Always work on a cool engine and replace plugs one at a time to avoid mixing up the spark plug wires. Be sure to check the spark plug gap with a feeler gauge before installation; for these engines with a High Energy Ignition (HEI) system, a common gap is around .035 to .045 inches, but always verify the spec for your specific engine.
Frequently Asked Questions (FAQ)
How often should I change the spark plugs?
For standard copper plugs, which are recommended for these vans, a replacement interval of every 20,000 to 30,000 miles is a good rule of thumb to maintain peak performance.
Do I need to check the gap on new spark plugs?
Yes, always. Even if plugs are advertised as 'pre-gapped,' they can be knocked out of spec during shipping. Use a spark plug gapping tool to ensure the gap matches your engine's requirements.
Should I use anti-seize on the threads?
This is a debated topic. Some plug manufacturers advise against it because their plugs have a special anti-seize coating. However, many mechanics use a very small amount on the threads when installing plugs into older cast-iron cylinder heads to prevent them from getting stuck. If you use it, apply a tiny dab and reduce the final torque setting slightly to avoid over-tightening.
What tools do I need to change my spark plugs?
You will need a ratchet, a few different lengths of socket extensions, a universal joint or 'wobble' extension, and a dedicated spark plug socket (usually 5/8" or 13/16" for these trucks). A spark plug gap tool is also essential.
Technical Specifications
OEM Part Numbers: 5613957
For most V8 applications (5.0L, 5.7L), the common spark plug is a 14mm thread, tapered seat, 5/8 inch hex, and a 0.433 inch reach. A popular OEM equivalent is the ACDelco R45TS. Always verify the correct plug for your specific engine.
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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.
- 🛍️ Shop This Part
- Signs of Failing Spark Plugs
- Choosing the Right Aftermarket Spark Plug
- Aftermarket Brand Tiers
- Pro Tip: Stick with Copper Plugs
- Known Issues & Recalls
- Installation Tips
- How often should I change the spark plugs?
- Do I need to check the gap on new spark plugs?
- Should I use anti-seize on the threads?
- What tools do I need to change my spark plugs?
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