Best Spark Plugs For 400 Small Block Chevy

When I first dropped a performance cam into my 400 small block Chevy (SBC 400), I quickly learned that the ignition system is only as strong as its weakest link. Choosing the right spark plugs for 400 small block Chevy isn’t just about making sure the thread fits; it’s about dialing in the heat range and conductivity to handle the specific demands of this legendary, often higher-compression engine. After testing various setups, here are the components—plugs and wires—that truly delivered consistent power and better throttle response.

IMAGE	PRODUCT NAME	AMAZON LINK
	NGK V Power Spark Plug UR4 (8 Pack) for GMC…	View on Amazon
	ACCEL 8179 HP Copper Spark Plug	View on Amazon
	NGK Standard Series Spark Plug YR5 (8 Pack) for CHEVROLET…	View on Amazon
	RLP Silicone Spark Plug Wires Set 8.0mm Black Replacement…	View on Amazon
	Universal Spark Plug Wire Set – 8.5mm Red High…	View on Amazon

NGK V Power Spark Plug UR4 (8 Pack) for GMC K3500 1979-1980 7.4L/454

The NGK V-Power plugs are often a go-to choice for classic street performance engines, and they work exceptionally well in the SBC 400 platform. The V-groove in the center electrode focuses the spark, promoting quicker ignition and better throttle response, which is particularly noticeable during aggressive acceleration. These are resistor plugs, helping to suppress ignition noise that can interfere with modern electronics, while the copper core ensures excellent heat transfer away from the firing tip.

Key features that stand out:
– Projected Insulator Type: Helps the plug reach operating temperature quickly, reducing fouling on street-driven motors.
– Electrode Tip Material: Nickel alloy offers durability and reliability.
– Heat Range: Manufacturer Heat Range 4 provides a good balance for mild to moderately tuned 400 SBCs.
– Copper Core: Aids in maximizing heat removal and conductivity.

Pros:
– Excellent conductivity thanks to the copper core.
– V-groove design improves ignitability.
– Good anti-fouling characteristics for street use.
– Strong reliability and consistent spark.

Cons:
– May not be ideal for extremely high-compression or race-only setups requiring a colder plug.

Best for: Daily driven or street/strip 400 SBCs running stock or mild performance setups where reliability and quick response are key.

Expert Opinion: NGK’s V-Power line offers a solid performance upgrade over standard stock plugs without the complexity or cost of platinum or iridium, making them a great value choice for the 400 Small Block Chevy.

ACCEL 8179 HP Copper Spark Plug

ACCEL has been a fixture in the performance ignition world for decades, and the 8179 HP Copper plug continues that tradition. These are straightforward, high-performance plugs designed to deliver a strong spark directly. Copper is still king when it comes to raw conductivity, making these plugs highly responsive. They often come pre-gapped, saving you a step during installation, although you should always check the gap against your engine’s specifications.

Key features that stand out:
– Ground Electrode Core Material: Copper for maximum electrical flow.
– Insulator Type: Mid projected design helps optimize heat range across various RPMs.
– Spark Plug Gap: Comes pre-gapped for convenience (though always verify).

Pros:
– Fantastic raw conductivity from the copper core.
– Budget-friendly performance option.
– Simple, reliable design.

Cons:
– Copper electrodes wear out faster than iridium or platinum plugs.

Best for: Budget-conscious builders or those running classic performance ignitions who prioritize conductivity over extreme longevity.

Expert Opinion: If you’re willing to change your plugs a little more frequently, these ACCEL copper units provide some of the best conductivity per dollar for your 400 small block. They handle high current well, especially when paired with a strong HEI distributor.

NGK Standard Series Spark Plug YR5 (8 Pack) for CHEVROLET K20 1978-1978 7.4L/454

Sometimes, the simplest solution is the best. The NGK Standard Series is the tried-and-true workhorse of ignition components. While these are listed for a Big Block application, their construction often makes them a reliable cross-reference for dependable, standard-heat-range 400 SBC applications, particularly those running close to stock compression and output. Their major advantage lies in their durability features, which ensure they don’t seize or corrode easily, a major benefit if you live in a humid climate.

Key features that stand out:
– Anti-corrosion plating: Trivalent metal plating resists corrosion and seizing, simplifying future plug changes.
– Insulation: Pure alumina silicate ceramic provides superior strength and heat transfer stability.
– Leak Prevention: Triple seals prevent combustion gas leakage.

Pros:
– Exceptionally good resistance to seizing and corrosion.
– Reliable heat transfer characteristics.
– Very durable construction suitable for long service life.

Cons:
– Does not offer the focused spark benefits of the V-Power design.

Best for: Stock rebuilds, daily drivers, or owners who prioritize long service intervals and ease of maintenance over maximum performance gains.

Expert Opinion: The YR5 plug is the reliable foundation. If your 400 small block Chevy is primarily a cruiser and you just want a reliable, trouble-free ignition system, you can’t go wrong with the robust build quality of the NGK Standard Series.

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

A performance plug means nothing if your wires can’t reliably deliver the high voltage. This RLP 8.0mm wire set is specifically built to complement the HEI (High Energy Ignition) systems often found on the 400 SBC. The heavy-duty silicone jacket shields the Kevlar spiral-wound core, ensuring maximum voltage delivery while minimizing dreaded electromagnetic interference (EMI/RFI), which is crucial for a clean running engine and reliable electronic gauges.

Key features that stand out:
– High Suppression: Provides extremely high EMI/RFI suppression alongside low resistance.
– Jacket Material: Heavy duty 8.0mm diameter silicone jacket resists heat, moisture, and chemicals.
– Fitment: Designed specifically for HEI Distributor systems in the 400 Small Block Chevy and other SBCs.

Pros:
– Excellent protection against heat and chemical damage.
– Low resistance ensures maximum spark energy reaches the plug.
– Great RFI suppression, essential for tuned engines.

Cons:
– Plug wire length adjustment may be required for some custom routing setups.

Best for: Anyone upgrading from old, cracked stock wires, especially if running a high-output HEI distributor on their 400 small block.

Expert Opinion: Never overlook the wires. These RLP wires offer a perfect balance of diameter (8.0mm is great for street use) and superior construction, ensuring that the spark energy generated by your coil actually reaches the plug tip efficiently.

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

If you’re pushing serious horsepower through your 400 small block—maybe running a hotter coil or higher compression—you need maximum insulation and minimum resistance. This 8.5mm wire set is designed for high-performance racing applications but works great on heavily modified street engines. The thicker 8.5mm silicone jacket and robust internal construction provide better protection against flashover and heat, ensuring a consistent spark even under extreme loads.

Key features that stand out:
– Design: 8.5mm spiral wound design for maximum voltage capacity.
– Construction: High di-electric strength insulator and tightly woven fiberglass braids provide superior heat resistance.
– Compatibility: Universal fit for HEI systems on both small block (SBC 400) and big block (BBC) engines.

Pros:
– Best high-temperature and oil resistance among the wires reviewed.
– Thicker insulation prevents voltage loss and flashover.
– Excellent conductivity for maximum spark delivery.

Cons:
– The 8.5mm diameter can be slightly bulky to route in tight engine bays.

Best for: High-performance, forced-induction, or high-compression 400 small block builds where maintaining spark integrity under high heat is critical.

Expert Opinion: The step up to 8.5mm is usually justified when you’ve upgraded the coil and ignition box. For a seriously modified 400 SBC, these wires ensure you don’t lose that precious voltage on its way to the plug.

Comparison and Practical Buying Advice

When selecting the best components for your 400 small block Chevy, you need to match the plug to your engine’s tune, and the wire set to your ignition strength.

If you have a mild street engine and just want reliable daily performance, the NGK Standard YR5 paired with the RLP 8.0mm wires offers fantastic value and durability. The anti-seizing properties of the NGK Standard plugs mean easier maintenance down the road.

For a street/performance tune where you’ve added headers, a performance cam, and a stronger coil, the NGK V Power UR4 or the ACCEL HP Copper plugs are superior choices due to their increased conductivity and better ignitability. The projected tip of the V Power plug is particularly good for reducing carbon buildup during low-RPM cruising.

If you’re running high compression or frequently engage in drag racing, focus on the ignition delivery first. Upgrade to the Universal 8.5mm High Performance wires to ensure zero flashover. Pair these with the copper plug of your choice (either NGK V Power or ACCEL) and confirm the heat range is appropriate—you might even need to step down to a colder plug than those reviewed here if you’re heavily modified. Remember, always check the recommended spark plug gap for your specific ignition setup before installation.

Final Verdict

Choosing the Best Spark Plugs For 400 Small Block Chevy really depends on how hard you drive it. For the average owner looking for a reliable boost in performance, the NGK V Power UR4 stands out as the best all-around plug, offering great design features (V-groove, copper core) without sacrificing reliability. For maximum energy delivery to complement that plug, pairing it with the RLP 8.0mm wire set is a winning, reliable combination for most street applications. If your 400 is strictly a high-output machine, invest in the Universal 8.5mm wires to handle the high energy demanded by performance coils.

Best Spark Plugs For 400 Small Block Chevy: Comprehensive FAQ

Q1: What is the recommended spark plug gap for a 400 Small Block Chevy with an HEI distributor?

A: Generally, the standard gap for a stock or mildly modified HEI system on a 400 SBC is around 0.045 inches. However, if you are running a high-output aftermarket coil and ignition box, you may be able to widen the gap slightly (up to 0.050 or 0.055 inches) to expose more of the fuel mixture to the flame front, though you must confirm your coil can reliably bridge this larger gap under load.

Q2: Why is the heat range of the plug so important for the SBC 400?

A: The heat range determines how quickly the spark plug transfers heat from the combustion chamber to the cooling system. Since the 400 SBC often runs hotter than its smaller brethren due to its siamese cylinder bores, choosing a plug with the correct heat range is crucial to prevent pre-ignition (plug running too hot) or fouling (plug running too cold). Most street applications use a standard or slightly cooler plug than stock if performance modified.

Q3: Should I use projected tip or non-projected tip spark plugs in my 400 Small Block?

A: A projected tip (like the NGK V Power) extends further into the combustion chamber, improving ignitability and helping the plug burn off carbon deposits at lower speeds (anti-fouling). These are great for street engines. Non-projected tips are typically used in very high-compression or racing engines where there is a risk of the piston hitting the extended tip, or where excessive heat demands a rapid transfer of heat.

Q4: Are copper core spark plugs better than iridium or platinum for a performance 400 SBC?

A: For raw, consistent performance and the strongest possible spark, copper core plugs are still often preferred because copper is the best electrical conductor. However, iridium and platinum last much longer. For a serious performance engine that sees frequent maintenance and plug changes, copper is an excellent choice for maximum power output.

Q5: Can I mix and match plug wires and spark plugs from different brands?

A: Yes, generally you can mix brands, provided the physical dimensions (thread reach, boot style) are compatible. The important factor is ensuring the plug wire resistance is low (typically under 500 ohms per foot) and the insulation (like the reviewed 8.0mm or 8.5mm silicone jackets) can handle the voltage delivered by your HEI distributor and coil.

Q6: How often should I check or replace my spark plugs and wires in my classic Chevy V8?

A: Copper plugs should typically be inspected every 10,000 to 15,000 miles, especially in a tuned 400 SBC. High-performance spark plug wires should be visually inspected annually for cracks, burns, or corrosion, and often replaced every 50,000 miles, or sooner if you frequently race the engine.