Top 7 Best Spark Plugs For 327 Chevy Reviewed 2025

When I bought my first classic 327 Chevy—a ’67 Nova—the first thing I noticed was the weak idle. We all know that choosing the best spark plugs for the 327 Chevy small block is crucial for getting that classic rumble and reliable horsepower. I’ve spent years dialing in these engines, and poor spark can tank your ignition performance and efficiency immediately. This guide covers seven tested options, from standard copper to modern iridium, ensuring your vintage iron runs strong and responsive.

IMAGE	PRODUCT NAME	AMAZON LINK
	NGK V-Power Spark Plug XR5 (8 Pack) Compatible With…	View on Amazon
	NGK Standard Series Spark Plug BR6S (8 Pack) for…	View on Amazon
	ACDelco Gold R45S (19362366) Conventional Spark Plug	View on Amazon
	NGK Iridium IX Spark Plug XR5IX (8 Pack) for CHEVROLET…	View on Amazon
	ACDelco CR43TS 5614029 (05614029) Professional Conventional…	View on Amazon
	NGK V-Power Spark Plug XR4 (8 Pack) Compatible With…	View on Amazon
	RLP Silicone Spark Plug Wires Set 8.0mm Black Replacement…	View on Amazon

NGK V-Power Spark Plug XR5 (8 Pack) Compatible With CHEVROLET CORVETTE 1962-1968 5.4L/327

These V-Power plugs are often the go-to choice for street-driven small-block Chevys, especially the robust 327. The unique V-groove design on the center electrode directs the spark towards the edge, improving ignitability and lowering the voltage requirements needed to fire the plug. This translates directly into more reliable cold starts and smoother idling, something every SBC owner appreciates. They maintain fantastic performance without breaking the bank.

Key features that stand out:
– Engine Family Chevy small block Gen I compatibility
– Original equipment manufacturer approved for reliable fitment
– V-Groove center electrode enhances ignition performance
– Increased fuel economy and lower emissions over standard plugs
– Resistor: Yes (helps suppress electronic noise)

Pros:
– Excellent ignition consistency for reliable street performance
– Great value and durability for a copper plug
– Works perfectly across the specified range of 327 models
– Resistor type prevents interference with modern electronics

Cons:
– Copper core requires replacement more frequently than Iridium

Best for:
Daily drivers and weekend cruisers looking for reliable, proven performance in a stock or lightly modified 327.

Expert Opinion: The XR5 designation means this is a medium heat range plug, ideal for most 327 SBC setups that run stock compression and carburetion, offering a great balance between fouling resistance and heat dissipation.

NGK Standard Series Spark Plug BR6S (8 Pack) for CHEVROLET C10 PICKUP 1964-1968 5.4L/327

Sometimes, sticking with the proven, traditional technology is the best route for an older engine. The NGK BR6S is a conventional copper core plug designed for standard reliability and robustness. Featuring a pure alumina silicate ceramic insulator, it excels at providing superior strength and maintaining optimal heat transfer away from the combustion chamber. If your classic 327 is a bare-bones cruiser or a workhorse truck, this plug offers fundamental dependability.

Key features that stand out:
– Trivalent metal plating provides superior anti-corrosion and anti-seizing properties
– Corrugated ribs prevent flashover across the insulator
– Pure alumina silicate ceramic insulator ensures excellent heat transfer
– Triple seals prevent leakage of combustion gases
– Copper core aids in heat removal

Pros:
– Highly resistant to corrosion, simplifying future plug changes
– Cost-effective choice for standard maintenance
– Excellent heat management characteristics
– Extremely simple and reliable design

Cons:
– Ignition stability can be slightly less precise than V-Power designs.

Best for:
Budget-conscious restorations, stock-spec engines, and SBC 327s used in classic trucks where conventional performance is sufficient.

Expert Opinion: The “6” heat range makes this a slightly “colder” plug compared to the XR5. While this is great for harder-running engines or those in hot climates, ensure your specific 327 doesn’t tend to foul plugs if it sees a lot of low-speed city driving.

ACDelco Gold R45S (19362366) Conventional Spark Plug

ACDelco is the traditional OEM choice for Chevy owners, and the Gold series (formerly Professional) maintains that legacy of quality. These conventional plugs are built tough, featuring a Black Onyx coating to fight corrosion, which is a major benefit when dealing with engine bays that might see occasional moisture or high heat. Their copper core ensures superb thermal conductivity, helping keep the plug durable under varying conditions typical of a classic 327.

Key features that stand out:
– Black Onyx coating helps significantly reduce corrosion
– Copper core provides great heat transfer and maximizes plug durability
– Ribbed suppressor seal extends resistance and helps prevent misfires
– Spark Plug Seat Style: Gasket
– Nickel-chrome alloy sheathing helps prevent corrosion on center electrode

Pros:
– Strong OEM heritage means great compatibility with SBC specs
– Excellent corrosion resistance due to the dual coatings
– Designed to handle general use reliability
– Ribbed design actively fights flashover

Cons:
– Standard technology doesn’t offer the lifespan of premium iridium plugs.

Best for:
Owners prioritizing original or conventional OEM-style parts and looking for robust, everyday reliability.

Expert Opinion: The R45S is a long-time favorite for vintage small blocks. It’s a slightly “hotter” plug (lower heat range) than the R44 series, often offering better low-speed combustion for standard street cars that might idle frequently.

NGK Iridium IX Spark Plug XR5IX (8 Pack) for CHEVROLET CHEVY II NOVA 1968-1968 5.4L/327

When you step into the world of high-performance ignition, Iridium is king. The NGK Iridium IX series is specifically designed for today’s high-demand engines, making it an excellent upgrade for a performance-built 327. The fine wire center electrode creates a consistent, powerful spark with minimal voltage draw. The Iridium alloy boasts an extremely high melting point, ensuring the plug stands up to serious heat and cylinder pressures generated by modified small blocks.

Key features that stand out:
– Fine wire Iridium center electrode ensures high durability and stable spark
– Iridium alloy has an extremely high melting point
– Perfect for today’s high-performance engines (and upgraded vintage ones)
– Engine V8, Engine Size 5.4L/327 specific fitment

Pros:
– Exceptional longevity—often lasting 3 to 4 times longer than copper plugs
– Significantly improved throttle response and idle stability
– Extreme resistance to wear and heat damage
– Requires lower ignition voltage to fire effectively

Cons:
– Premium price point compared to copper alternatives.

Best for:
Performance builds, engines with higher compression ratios, or owners who demand the longest lifespan and best possible ignition efficiency.

Expert Opinion: While traditionalists often stick to copper, the narrow electrode of Iridium dramatically improves the efficiency of the spark, which is highly beneficial in older, carburetor-fed engines where clean combustion is sometimes a challenge.

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

This ACDelco option provides reliable, conventional performance in a convenient box of 8, simplifying the job for the 327 owner. Like other ACDelco offerings, the CR43TS uses a high-quality copper core to ensure great heat transfer, crucial for preventing engine misfires caused by overheating. It’s a solid, no-nonsense choice for reliable operation and standard maintenance.

Key features that stand out:
– Copper core thermal properties provide great heat transfer
– Features a ribbed suppressor seal which prevents flash-over and misfire
– Black onyx coating helps prevent corrosion
– Increased plug durability through quality construction

Pros:
– Excellent value when purchased in the 8-pack box
– Reliable conventional performance for stock applications
– Effective protection against corrosion and misfires
– Simple to gap and install

Cons:
– A relatively “hot” plug, meaning careful heat range consideration is needed for aggressive driving.

Best for:
Stock 327 engines that primarily see street use and need a dependable, cost-effective replacement plug.

Expert Opinion: The heat range “4” in the CR43TS indicates a hotter running plug, which is often beneficial for engines that might burn a little oil or see a lot of short trips where cylinder temperatures need to climb quickly to prevent fouling.

NGK V-Power Spark Plug XR4 (8 Pack) Compatible With CHEVROLET CHEVY II NOVA 1965-1967 5.3L/327

The NGK V-Power XR4 is structurally similar to the XR5 reviewed earlier, but its heat range designation is slightly different. The XR4 is a “hotter” plug (lower heat range number), making it specifically tailored for slightly milder running conditions or earlier model 327 engines where better fouling resistance is necessary. It still benefits from the V-groove design, boosting ignitability and maintaining smooth idle characteristics.

Key features that stand out:
– Engine V8, Engine Size 5.3L/327 specific fitment
– Manufacturer Heat Range: 4 (a hotter plug than the XR5)
– Original equipment manufacturer approved
– Increased fuel economy and lower emissions
– Resistor: Yes

Pros:
– Excellent choice for preventing carbon fouling in mild 327s
– V-groove technology provides reliable ignition
– Solid V-Power construction and durability
– Good plug for colder climates or engines that idle extensively

Cons:
– Might run too hot if your engine is heavily modified or experiences sustained high RPMs.

Best for:
Early model 327s, low-compression engines, or vehicles used heavily in stop-and-go traffic where avoiding plug fouling is the priority.

Expert Opinion: Choosing between the XR4 and XR5 often depends on your engine’s overall health and operating environment. If your current plugs tend to look oily or black after a few thousand miles, the XR4 heat range might be the ideal solution.

RLP Silicone Spark Plug Wires Set 8.0mm Black Replacement for Chevy GMC Small Block SBC HEI Distributor Valve Cover Wires 265 267 283 302 305 307 327 350 400

While not a spark plug, your ignition system is only as good as the weakest link, and often that’s the tired, old plug wires. This RLP set is a critical component for maximizing the performance of any plug you choose for your 327. Designed for Small Block Chevy GMC engines, these 8.0mm heavy-duty silicone wires offer extremely high suppression of electromagnetic interference (EMI/RFI) while maintaining very low resistance, ensuring maximum spark energy reaches the plug tip.

Key features that stand out:
– Heavy duty 8.0mm diameter silicone jacket protects against heat, moisture, and chemicals
– Extremely high EMI/RFI suppression with very low resistance
– Fit for Small Block Chevy GMC (including 327, 350, 400) with HEI systems
– Premium Quality stainless steel and brass terminals for excellent conductivity
– 90-degree boot angles at both cap and plug for optimal fitment

Pros:
– Essential upgrade for better spark transmission
– Superior protection against engine bay elements and heat
– Reduces electrical noise, important if you run modern audio systems
– Compatible with common HEI distributor setups

Cons:
– Does not include the coil wire (must be purchased separately).

Best for:
Any 327 owner running an HEI ignition system who wants to ensure 100% of the ignition power reaches their new spark plugs.

Expert Opinion: Installing new, high-quality plugs with old, worn wires is a waste of money. These wires effectively manage resistance and protect the spiral core, which is vital for maintaining high voltage under load.

Comparison Insights: Choosing the Right Plug for Your 327

When sifting through these top options for your 327 small block, the choice usually boils down to technology and heat range.

For classic street reliability, the ACDelco offers excellent conventional reliability and fantastic anti-corrosion properties, making the R45S a traditional solid performer. They are a great match if you are sticking strictly to factory specs.

If you want a slight upgrade in efficiency without jumping to expensive materials, the NGK V-Power provides slight efficiency gains for street driving thanks to its unique electrode design. The V-Power XR5 is the safer “medium” heat choice, while the XR4 is better if your engine tends toward fouling.

However, if you’re building a high-compression or heavily modified 327—or just want maximum longevity—Iridium plugs like the XR5IX are a must-have due to their extreme durability and consistent spark. They handle higher cylinder pressures and heat far better than conventional copper cores.

Finally, remember that the RLP Spark Plug Wires are crucial system upgrades. A high-performance plug combined with old wires won’t deliver its full potential. Wires are key to ensuring maximum voltage transfer.

Final Verdict: Our Recommendations for the 327 Chevy

Choosing the right spark plug depends entirely on how you drive and the state of tune your classic 327 is in. Here are my top recommendations, broken down by application:

For the Classic Street Cruiser (Stock to Mild Tune):

Go with the NGK V-Power Spark Plug XR5. This plug offers the best balance of reliable V-groove ignition, durability, and a medium heat range suitable for most well-maintained 327s on pump gas. It’s an efficient, cost-effective workhorse.

For High-Performance Builds (High Compression or Forced Induction):

The clear winner is the NGK Iridium IX Spark Plug XR5IX. Its exceptional resistance to heat, erosion, and fouling ensures that your spark remains stable and strong, even under the stress of high RPMs and aggressive timing. This longevity is worth the investment.

The Essential System Upgrade:

Regardless of which spark plug you select, you should pair it with the RLP Silicone Spark Plug Wires Set. Upgrading the wires ensures that the power created by your coil and distributor actually gets delivered cleanly to your new plugs, completing the system upgrade.

Best Spark Plugs For 327 Chevy: Frequently Asked Questions

Q1: What is the correct gap setting for a small block Chevy 327?

A: The standard gap setting for a stock, points-ignition 327 is generally between 0.030 and 0.035 inches. However, if you have upgraded to a High Energy Ignition (HEI) system or aftermarket electronic ignition, you can usually increase the gap to 0.040 or even 0.045 inches to take advantage of the stronger spark delivery. Always check the plug manufacturer’s recommendation for maximum performance.

Q2: How important is the heat range when choosing plugs for the 327 Chevy?

A: The heat range is critical. It refers to the plug’s ability to transfer heat away from the combustion chamber. A “hotter” plug (lower number, e.g., NGK XR4) retains more heat and is better for low-speed street driving to prevent carbon fouling. A “colder” plug (higher number, e.g., NGK BR6S) transfers heat faster and is essential for high-performance or high-compression engines to prevent pre-ignition and melting.

Q3: Should I use copper or iridium spark plugs in my classic 327?

A: Both are excellent options. Copper core plugs (like the NGK V-Power or ACDelco conventional options) are traditional, effective, and cost much less. They are ideal for engines seeing limited use. Iridium plugs (like NGK Iridium IX) offer superior durability, require replacement less often, and provide a more focused, consistent spark, making them the choice for high-mileage drivers or performance builds.

Q4: Are resistor plugs necessary for an old engine like the 327?

A: If your 327 has modern electronic components like an aftermarket radio, digital gauges, or an electronic ignition system (like HEI), resistor plugs are highly recommended. They contain a resistor that suppresses electromagnetic interference (EMI/RFI) created by the spark, preventing static or noise in your electronics. Most modern plugs, including the NGK V-Power series, are resistor types.

Q5: How often should I change my spark plugs in a small block Chevy 327?

A: This depends on the plug material and how you drive. For standard copper plugs, replacement every 10,000 to 15,000 miles is typical for optimal performance. If you switch to high-end iridium plugs, you can expect lifespans extending to 40,000 miles or more, depending on your tuning and engine condition.

Q6: Do I need special spark plug wires for my 327 HEI ignition?

A: Yes, upgrading your spark plug wires is crucial if you run an HEI system. HEI produces higher voltage than traditional points distributors, requiring wires that have a thicker silicone jacket (like the RLP 8.0mm set) and low resistance to handle the extra current efficiently without leakage or insulation breakdown.