What is the spark plug gap on a 57 Vortec?
The spark plug gap for a 5.7L Vortec is typically 0.040 inches (1.0 mm).
While this is the standard spec for many stock configurations, the exact gap can vary with year, model, and spark plug type. This article explains the common spec, how to check it, and what to consider when using non-standard plugs or modifications.
Typical gap specification for the 5.7L Vortec
The standard gap used by GM for the 5.7L Vortec is generally 0.040 inches (1.0 mm). Some spark plugs may be pre-gapped differently; always verify with the plug manufacturer or GM service documentation for your specific application.
Note: The gap can differ if you are using certain performance plugs, iridium or platinum types, or if you have a special tune; in those cases, refer to the plug's gap specification and adjust if recommended.
To ensure accurate measurement and adjustment, follow the steps below.
Follow these steps to measure and adjust the gap correctly on a 5.7L Vortec engine:
- Ensure the engine is cool and the ignition is off. If possible, disconnect the negative battery terminal for safety.
- Remove the spark plug wire or ignition coil boot to access the spark plug.
- Inspect the spark plug for wear or damage and confirm you are using the correct heat-range plug for your engine.
- With a proper spark plug gap gauge, measure the gap between the center electrode and the ground electrode.
- Set the gap to 0.040 inches (1.0 mm). If widening, carefully bend the ground electrode; if narrowing, gently bend the center or ground electrode as needed. Recheck the gap after each adjustment.
- Reinstall the spark plug and tighten to the manufacturer’s torque specification for your plug size and vehicle. Reconnect the ignition wire/coil boot.
- Run the engine and check for smooth operation; if misfires occur, recheck the gap and inspect ignition components.
Always verify the gap with the recommended plug type and refer to GM service manuals or the plug manufacturer for exact torque specs and year-specific notes. If you have modified the engine or upgraded to a different plug type, gap requirements may differ slightly.
Special considerations
Plug type and modifications
Iridium and platinum plugs are often pre-gapped, but newer or performance-grade plugs may require a different gap. Always confirm the recommended gap from the plug manufacturer, especially if you are using aftermarket plugs or an engine tune that could affect ignition timing.
If your vehicle has a custom tune, custom ignition system, or has undergone significant modifications, consult the service manual or a professional to determine if a different gap is warranted.
Summary
For most stock 5.7L Vortec engines, the target spark plug gap is 0.040 inches (1.0 mm). Always verify the exact specification for your year and plug choice, and follow proper procedure when checking and adjusting the gap to ensure reliable ignition and engine performance.
Is a 7 or 8 spark plug hotter?
A spark plug with a heat range 7 is hotter than a heat range 8 plug, meaning it retains heat longer and dissipates it more slowly. An #8 plug is "colder" and transfers heat to the cylinder head more quickly. The best choice depends on the engine's application, with hotter plugs (like a #7) suitable for daily driving and colder plugs (like an #8) ideal for high-performance engines, forced induction, or high-RPM use to prevent detonation.
This video explains the difference between hot and cold spark plugs: 50sHigh PSI tvYouTube · May 3, 2019
Spark plug heat range 7 vs. 8
| Feature | Heat Range 7 | Heat Range 8 |
|---|---|---|
| Heat | Hotter | Colder |
| Heat Transfer | Slower heat transfer to the cylinder head | Faster heat transfer to the cylinder head |
| Insulator Nose | Longer insulator nose | Shorter insulator nose |
| Best For | Stock, daily-driven, or less aggressive engines that run at lower RPMs | High-performance, high-compression, or forced-induction engines (like turbocharged or supercharged) |
| Risk | Can cause engine knocking or detonation if the engine runs too hot for the plug | Can cause carbon fouling if the engine doesn't get hot enough for the plug to "self-clean" |
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What is the spark plug gap on a 5.7 V8?
For the 5.7L Hemi V8 engine, the spark plug gap typically ranges between 0.040 and 0.043 inches (1.016 to 1.092 mm), depending on the specific year and model of the vehicle.
What is the spark plug gap on a 5.7 350 Chevy?
The spark plug gap for a 5.7L 350 engine is typically between 0.0350.0350.035 and 0.0450.0450.045 inches, but it's best to confirm the exact specification for your specific year and model in the owner's manual. While 0.0350.0350.035 is a common factory gap, some vehicles, especially those with a modern high-performance ignition system, may recommend a gap closer to 0.0400.0400.040 inches.
You can watch this video to learn how to check and adjust the spark plug gap: 58sMossMan381YouTube · Nov 5, 2016
- Common gap: A typical range is 0.0350.0350.035 to 0.0450.0450.045 inches.
- Standard recommendation: For many stock applications, the gap is often set at 0.0350.0350.035 inches.
- Higher performance applications: Some performance setups or newer GM engines may call for a gap of around 0.0400.0400.040 inches.
- How to verify: Always consult your vehicle's owner's manual or the manufacturer's specifications to ensure you have the correct gap for your specific engine.
- Why it matters: An incorrect gap can cause misfires, poor fuel economy, and rough running.
What is the spark plug gap on a 57 Chevy 283?
Spark plug gap should be set between 0.035 and 0.040 inches to ensure proper combustion.
