Best Spark Plugs For 427 Chevy – 5 Options Reviewed

When I dropped the new 427 big block into my project car, I quickly learned that the right ignition components are absolutely critical for getting that legendary torque to the pavement. Finding the best spark plugs for 427 Chevy setups—especially when running a modified ignition or HEI distributor—requires balancing the correct heat range, durability, and material quality. I’ve put together this guide reviewing some of the top-tested options, including essential plug wires, to help your big block ignition fire strong and consistently.

IMAGE	PRODUCT NAME	AMAZON LINK
	NGK V-Power Spark Plug GR5 (8 Pack) Compatible With…	View on Amazon
	ACDelco GM Original Equipment R45TS (19354415) Conventional…	View on Amazon
	ACDelco CR43TS 5614029 (05614029) Professional Conventional…	View on Amazon
	Universal Spark Plug Wire Set – 8.5mm Red High…	View on Amazon
	JDMSPEED New HEI Red Spiral Core Spark Plug Wires 45…	View on Amazon

NGK V-Power Spark Plug GR5 (8 Pack) Compatible With CHEVROLET CORVETTE 1968-1969 7.0L/427

For many performance enthusiasts, NGK is the gold standard for reliable ignition, and these V-Power plugs are perfectly tailored for classic big block specs. If you’re running a street engine close to stock specifications but want improved reliability and better resistance to fouling, these are a superb choice. The unique V-grooved center electrode enhances ignitability by reducing quenching, meaning you get a strong, clean spark where you need it most. They are a dependable option that respects the Chevy big block Mark IV heritage.

Key features that stand out:

• Original equipment manufacturer approved: Ensures proper fit and function for the 427.
• V-Grooved Center Electrode: Improves ignition and helps lower potential misfires.
• Resistor: Built-in resistor helps suppress RFI (radio frequency interference).
• Heat Range: Manufacturer Heat Range 5, suitable for standard to moderately performance-built engines.

Pros:
– Excellent quality control and reliable performance.
– Good resistance to fouling.
– Affordable without sacrificing performance quality.

Cons:
– Might require a colder heat range if running very high compression or forced induction.

Best for: Reliable street performance and historically accurate engine rebuilds requiring a high-quality standard plug replacement.

Expert Opinion: NGK V-Power plugs provide phenomenal value by offering superior ignitability over basic conventional plugs due to the unique electrode design, making them a safe and effective upgrade for the 427.

ACDelco GM Original Equipment R45TS (19354415) Conventional Spark Plug

When maintaining an authentic 427, many owners prefer sticking with ACDelco because they are true GM Original Equipment (OE). The R45TS is a time-tested plug designed specifically for these motors, offering the classic reliability and robust structure you expect. This conventional plug uses a high-conductivity copper core, which is essential for maximizing heat transfer away from the tip, helping to maintain durability even under spirited driving conditions.

Key features that stand out:

• Copper Core: Provides maximum heat transfer, crucial for durability in a high-output big block.
• Black Onyx Coating: Applied to the metal shell to reduce corrosion, extending the plug’s service life.
• Ribbed Suppressor Seal: Prevents spark ‘flash over,’ ensuring the spark stays where it belongs and preventing misfires.
• Nickel-Chrome Sheathing: Protects the center electrode from premature corrosion.

Pros:
– True GM OE fit and performance.
– Excellent durability and corrosion resistance.
– Reliable heat dissipation features.

Cons:
– A basic conventional plug, lacking the advanced electrode materials of iridium or platinum plugs.

Best for: Enthusiasts seeking OE parts for restoration projects or those prioritizing long-term durability in a naturally aspirated 427.

Expert Opinion: The R45TS is the benchmark plug for many classic Chevy big block engines. Its design focuses on reliable, consistent performance and excellent heat management, making it hard to beat for stock or mild street applications.

ACDelco CR43TS 5614029 (05614029) Professional Conventional Spark Plug BOX OF 8

The CR43TS is another highly regarded conventional plug from ACDelco, often categorized under their Professional line, which means it meets strict standards for reliable aftermarket replacement. Similar to the R45TS, it uses a high-quality copper core for effective thermal performance, but this specific heat range (indicated by the “43”) might be a slightly colder option than the R45TS, depending on your engine’s tune and climate. This plug is built to handle the demands of the 7.0L/427 engine with excellent suppression of flash-over and corrosion protection.

Key features that stand out:

• Professional Grade Quality: Ensures reliable performance for mechanics and serious DIYers.
• Copper Core: Provides necessary heat transfer properties for increased durability.
• Ribbed Suppressor Seal: Prevents potential misfires by keeping the spark path isolated.
• Black Onyx Coating: Aids in preventing corrosion of the metal shell, especially important in humid or marine environments.

Pros:
– Strong thermal properties for consistent running.
– Designed for superior resistance against fouling and corrosion.
– Sold in a convenient box of 8 for immediate full replacement.

Cons:
– Heat range must be carefully confirmed to match your specific engine build.

Best for: Performance rebuilds or drivers needing a slightly colder plug option than the standard R45TS to accommodate slight compression bumps or richer mixtures.

Expert Opinion: When stepping up from the basic OE plug, the Professional series like the CR43TS often offers marginally better build quality and consistency. Always verify the required heat range for your specific 427 big block specs before installing.

Universal Spark Plug Wire Set – 8.5mm Red High Performance – Compatible with Chevy GM SBC BBC Engines Small Block 305 307 327 350 Big Block 427 454 502 and More with HEI Distributor

A fantastic spark plug is useless without the proper wiring to deliver the energy. This 8.5mm high-performance wire set is crucial for maximizing the output of your chosen plugs, especially when running an HEI (High Energy Ignition) distributor on your 427. The large 8.5mm diameter and spiral wound design ensure extremely low resistance, meaning more voltage gets to the spark plug tip, resulting in a hotter, more efficient spark and reduced chance of ignition breakdown under load.

Key features that stand out:

• 8.5mm Spiral Wound Design: Maximizes energy transfer and minimizes electrical resistance.
• High Temperature Silicone Jackets: Heavy-duty silicone protects against oil, abrasion, and intense heat from the engine bay.
• Universal Compatibility: Designed to fit HEI distributors common on Big Block Chevy (BBC) engines, including the 427 and 454.
• 90 Degree Boots: Features 90-degree boots on both ends, optimized for clearance around exhaust manifolds and headers.

Pros:
– Excellent conductivity for maximum spark energy.
– Extremely durable, high di-electric strength insulator.
– Easy to install with clear compatibility for BBC HEI systems.

Cons:
– Red color may not suit all engine bay aesthetics.

Best for: Any 427 running an upgraded HEI distributor setup and requiring maximum spark delivery for performance.

Expert Opinion: Don’t skimp on wires when optimizing your 427’s ignition. The difference between stock wires and a quality 8.5mm set like this is immediately noticeable in throttle response and high-RPM stability.

JDMSPEED New HEI Red Spiral Core Spark Plug Wires 45 Degree End 396-427-454-502 Replacement for Chevy BBC

If you need quality wires specifically for your Big Block Chevy but prefer a different boot angle or are working with a slightly tighter budget, this JDMSPEED set is a strong contender. These 8mm spiral core wires are specifically targeted at BBC engines, ensuring a straightforward replacement for your 396-427-454-502 ignition system. A key selling point is the high-temperature boots that can withstand substantially more heat than standard plug boots, which is a big relief when working near hot headers.

Key features that stand out:

• 8mm Spiral Core Wires: Low resistance (only 270 Ohms per foot) ensures powerful spark delivery.
• High-Temperature Boots: Black boots are rated to withstand 50 degrees more heat than conventional options.
• 45 Degree End: Provides flexibility and clearance in tight engine bays compared to standard 90-degree boots.
• Quality Guaranteed: Built for replacement on HEI systems common in BBC engines.

Pros:
– Excellent heat resistance at the spark plug end.
– Very low resistance for strong spark.
– Provides a cost-effective performance upgrade.

Cons:
– 8mm diameter is slightly smaller than the 8.5mm high-end competitors.

Best for: Budget-conscious BBC owners needing robust, heat-resistant wires that are guaranteed to work with HEI setups and offer good clearance via the 45-degree boot angle.

Expert Opinion: While slightly narrower than the thickest wires available, 8mm spiral core wires with low resistance are more than sufficient for street 427s. The added heat protection in the boots makes these particularly beneficial if you have tight header clearance.

Helpful Comparison Short Insights

Choosing the right components for your 427 big block means understanding subtle differences. Regarding the actual spark plugs, the ACDelco R45TS is the standard OE replacement plug, known for its proven track record and classic heat range, making it a reliable choice for unmodified engines. If you notice signs of detonation or are running a slight compression bump, the ACDelco CR43TS may offer a subtly colder heat range, enhancing detonation resistance.

The NGK V-Power GR5 is arguably the best overall performance plug here for a street motor, offering enhanced ignitability through its V-groove design, often resulting in slightly better idle quality and fuel burn compared to standard conventional plugs.

When it comes to the required spark plug wires, the difference is primarily in thickness and boot angle. The 8.5mm Red High Performance Set offers the lowest resistance and highest voltage carrying capacity, making it ideal for maximized performance builds. Conversely, the JDMSPEED 45 Degree Wires are excellent for clearance issues and offer superior heat resistance at the boots, a major benefit if your headers run close to the spark plugs.

Final Verdict

If you’re looking for the single best overall setup for a typical street-driven 427 Chevy Big Block, we recommend pairing the NGK V-Power Spark Plug GR5 with the Universal 8.5mm Red High Performance Wire Set. This combination offers excellent ignitability and maximum energy delivery, ensuring your big block runs strong and clean.

If you are restoring the engine and value originality, the ACDelco GM Original Equipment R45TS is the correct conventional plug to maintain that OE appearance and performance standard.

Finally, for the racer or weekend warrior pushing higher compression, starting with a colder plug like the ACDelco CR43TS provides an excellent baseline for tuning, ensuring you have the thermal headroom necessary for demanding conditions.

Best Spark Plugs For 427 Chevy FAQs

What is the correct spark plug gap for a 427 Chevy Big Block?

The optimal gap depends heavily on your ignition system. For a stock points ignition, the gap is usually set around 0.035 inches. However, if you are running a high-output HEI distributor (which is common for performance 427s), you can generally open the gap up to 0.045 inches or even 0.050 inches. Always consult your engine builder or the ignition manufacturer’s recommendations when using high-performance wires.

Should I choose a conventional, platinum, or iridium spark plug for my 427?

For classic high-performance engines like the 427 big block, many experts still prefer high-quality conventional copper-core plugs (like the ACDelco or NGK V-Power options listed). Copper is an excellent conductor and dissipates heat effectively. Platinum and iridium plugs are designed for long life in modern computerized engines, but they often don’t provide a measurably better spark and can sometimes complicate tuning in older, high-compression motors.

How often should I replace the spark plugs in my classic 427 engine?

Because 427s typically run conventional plugs, they wear faster than modern long-life materials. If your 427 is used mainly for performance driving or frequent cruising, aim to check and replace the plugs every 10,000 to 12,000 miles or at least once per racing season to maintain peak ignition performance.

Why are high-performance spark plug wires necessary for a 427 big block with an HEI distributor?

The HEI (High Energy Ignition) system is designed to produce a significantly higher voltage spark compared to older points systems. To efficiently deliver that increased voltage to the 427’s spark plugs without energy loss or misfire, low-resistance, high-di-electric strength wires (like the 8mm or 8.5mm spiral core sets) are essential. They prevent “flash over” and ensure maximum spark intensity.

What is “heat range,” and how does it relate to the 427 Chevy?

Heat range measures how quickly the spark plug transfers heat from the tip to the cooling system. A “hot” plug burns off deposits quickly but can cause pre-ignition in a hot engine. A “cold” plug dissipates heat quickly, reducing the chance of pre-ignition in a high-compression big block Chevy but risks fouling at low RPMs. If you’ve modified your engine for more power, you will likely need a slightly colder plug than the factory specification.

Can I mix spark plug brands with my existing wires?

Yes, as long as the plug wires are designed for the correct distributor type (usually HEI or conventional) and the correct end terminal (which is standard for most 427 applications), you can mix brands. The critical factor is ensuring the plug has the proper fit (reach, thread size) and, most importantly, the correct heat range for your specific 427 Chevy engine configuration.