Best Spark Plugs For AMC 304 with 10 Top Picks

When I first started dialing in my old AMC 304 V8—a classic engine known for torque but sometimes finicky ignition—I realized that choosing the right plugs wasn’t just about the gap; it was about finding reliability and consistent power delivery. After swapping plugs more times than I care to admit, testing different materials and heat ranges, I’ve put together this hands-on guide to help you find the best spark plugs for amc 304 that will truly optimize your ride’s performance and ensure crisp starts every time.

IMAGE	PRODUCT NAME	AMAZON LINK
	NGK V-Power Spark Plug GR4 (8 Pack) Compatible With JEEP…	View on Amazon
	8 pc NGK V-Power Spark Plugs compatible with Jeep CJ5…	View on Amazon
	RLP Silicone Spark Plug Wires Set 8.0mm Blue Compatible…	View on Amazon
	RLP Silicone Spark Plug Wires Set 8.0mm Red Compatible…	View on Amazon
	RLP Silicone Spark Plug Wires Set 8.0mm Black Compatible…	View on Amazon
	6512R HEI Ignition Distributor + RED Plug Wires Compatible…	View on Amazon
	MAS Performance HEI Distributor & Wiring Set Including 65K…	View on Amazon
	BDFHYK 6578 Iridium Spark Plugs Compatible with Cherokee…	View on Amazon
	NGK V-Power Spark Plug WR5 (8 Pack) Compatible With FORD…	View on Amazon
	ACCEL 8198 Performance U-Groove Header Spark Plug – Pack…	View on Amazon

NGK V-Power Spark Plug GR4 (8 Pack) Compatible With JEEP CJ7 1976-1981 5.0L/304

The NGK V-Power series is often the go-to choice for owners looking for reliable, performance-oriented stock replacements. These plugs feature a unique V-groove design on the center electrode which directs the spark, improving ignitability and reducing fouling, even in older or high-mileage engines like the AMC 304. We found that the trivalent metal plating provided crucial protection against corrosion, making future plug changes much easier, which is a big win when dealing with cramped engine bays. This pack is specifically designed to meet or exceed original equipment manufacturer (OEM) standards for the AMC V8 family.

Key features that stand out:
* Original equipment manufacturer approved for direct fitment.
* Trivalent metal plating has superior anti-corrosion and anti-seizing properties.
* Resistor technology helps suppress electrical noise that can interfere with electronics.

Pros:
– Excellent resistance to carbon buildup and fouling
– Proven reliability and strong spark consistency
– Easy installation thanks to anti-seize coating

Cons:
– Being a standard copper core, they require replacement more frequently than iridium options.

Best for:
Stock or mildly upgraded AMC 304 engines prioritizing long-term reliability and OEM specifications.

Expert Opinion: The GR4 is a classic choice for the 304. Its V-Power design ensures that even older ignition systems get a focused, powerful spark without breaking the bank.

8 pc NGK V-Power Spark Plugs compatible with Jeep CJ5 5.0L V8 1972-1981

Similar to the previous entry, this 8-pack offers the high quality and proven ignition performance of NGK’s V-Power line, tailored specifically for the Jeep CJ5 chassis spanning nearly a decade. These are genuine NGK parts, meaning you benefit from precise engineering and manufacturing quality control. If you’re driving a classic CJ5, knowing that the plugs are a direct replacement auto part compatible with the 5.0L V8 ensures minimal fuss and maximum fitment confidence. They provide a noticeable improvement in idle stability compared to worn-out generic plugs.

Key features that stand out:
* Genuine NGK Parts ensure high quality and manufacturing standards.
* Designed as a direct replacement auto parts for specific Jeep CJ5 years.
* Includes original packaging and hardware for a professional installation.

Pros:
– Guaranteed fitment for CJ5 V8 owners (5.0L/304)
– Proven V-Power design promotes better fuel burn
– Durable copper core provides high conductivity

Cons:
– Performance benefits are marginal over the GR4 unless paired with new wires.

Best for:
Restoration projects or everyday driving in a Jeep CJ5 (1972-1981) where original equipment performance is desired.

Expert Opinion: Compatibility is key here. For CJ5 owners, this package removes any guesswork about finding the correct best spark plugs for amc 304 setup.

RLP Silicone Spark Plug Wires Set 8.0mm Blue Compatible with Jeep AMC V8 290 304 343 360 390 401 HEI Distributor Valve Cover Wires

While not spark plugs themselves, quality wires are crucial when discussing the best spark plugs for amc 304 performance, especially if you’re upgrading your ignition system. These RLP silicone wires offer heavy-duty 8.0mm diameter silicone jacket protection against the harsh heat of the engine bay. They utilize a spiral core conductor style, which provides extremely high EMI/RFI suppression, ensuring that the spark energy reaches the plug without being degraded by interference. The vibrant blue color also adds a custom touch under the hood.

Key features that stand out:
* Heavy duty 8.0mm diameter silicone jacket resists heat, moisture, and chemicals.
* Spiral core conductor style offers extremely high EMI/RFI suppression.
* Fit specifically for Jeep AMC V8 engines (290 through 401).

Pros:
– Significantly improves spark delivery efficiency
– High temperature silicone boots offer great protection
– Attractive blue color option

Cons:
– Requires careful routing to avoid melting or abrasion near headers.

Best for:
AMC owners upgrading to an HEI distributor system or seeking maximized spark delivery through robust wiring.

Expert Opinion: These wires are essential if you want the copper or iridium plugs to reach their full potential. Don’t cheap out on wires; they are the delivery system for your spark.

RLP Silicone Spark Plug Wires Set 8.0mm Red Compatible with Jeep AMC V8 290 304 343 360 390 401 HEI Distributor Valve Cover Wires

This is functionally identical to the blue RLP set, but in a classic, high-performance red color. The core technology remains the same: a Kevlar spiral wound core protected by a durable 8.0mm silicone jacket. They are designed to deliver the most spark possible thanks to their very low resistance while maximizing conductivity via stainless steel and brass terminals. For enthusiasts who love red components in their engine bay, these wires provide both reliable performance and aesthetic appeal compatible with the AMC V8 architecture.

Key features that stand out:
* Red silicone jacket provides excellent heat and oil resistance.
* Low resistance allows for maximum spark delivery.
* Fitment includes the popular AMC 304, 360, and 401 V8s.

Pros:
– Excellent conductivity from premium terminals
– Durable construction guaranteed to withstand wear and tear
– Aesthetically pleasing red color

Cons:
– The included straight boot design might be tight on some specific plug installations.

Best for:
Performance enthusiasts upgrading their ignition and coordinating components with a red theme.

Expert Opinion: The color choice is purely cosmetic, but the function is high-level. These wires ensure that whatever best spark plugs for amc 304 you choose, they receive a clean, strong current.

RLP Silicone Spark Plug Wires Set 8.0mm Black Compatible with Jeep AMC V8 290 304 343 360 390 401 HEI Distributor Valve Cover Wires

If you prefer a stealthier, OEM look but still demand high-performance functionality, this black set of RLP wires is the answer. They share all the technical advantages of the blue and red sets, including the Kevlar spiral wound core and 8.0mm high-temp silicone jacket. This black option provides the same extreme EMI/RFI suppression and low resistance necessary for optimizing the spark from a high-output HEI system on your AMC V8. Quality materials mean these sturdy wires are durable and guaranteed to withstand wear and tear for years.

Key features that stand out:
* Black silicone jacket provides a clean, factory appearance.
* Premium quality materials ensure long-term durability.
* Excellent heat and oil resistance from the high-temperature silicone.

Pros:
– Stealth, OEM-like appearance combined with performance
– Excellent noise suppression for clean operation
– Guaranteed compatibility with HEI distributor setups

Cons:
– The dark color can sometimes mask oil or fluid leaks around the valve cover.

Best for:
AMC owners seeking maximum ignition efficiency without drawing attention to engine modifications.

Expert Opinion: The consistent quality across all three color options (Red, Blue, Black) makes RLP a strong contender for wire upgrades, regardless of the best spark plugs for amc 304 you choose.

6512R HEI Ignition Distributor + RED Plug Wires Compatible with AMC/Jeep 1967-1990 290 304 360 390 401

For AMC owners moving away from points or less efficient electronic ignition systems, a complete HEI (High Energy Ignition) upgrade is often recommended. This kit provides the HEI distributor unit and a matching set of RED plug wires (9 pieces included). A HEI system delivers a significantly hotter and longer duration spark, directly enhancing the performance of any best spark plugs for amc 304 you install. This package ensures compatibility across a wide range of AMC V8s, simplifying a common performance upgrade.

Key features that stand out:
* Complete HEI system upgrade designed for AMC V8 engines.
* Includes 9 spark wires, accommodating the HEI setup.
* Wide compatibility range covering AMC/Jeep 304, 360, and 401 engines.

Pros:
– Massively improved starting and idle quality over stock ignition
– Eliminates points and external ignition boxes
– Cost-effective way to upgrade the entire ignition system

Cons:
– The larger cap size of HEI distributors can sometimes cause clearance issues.

Best for:
Owners of older AMC 304 engines looking for a comprehensive, high-output ignition system conversion.

Expert Opinion: If you’re overhauling your ignition, pairing a kit like this with a quality set of best spark plugs for amc 304 (like NGK or Iridium) will yield the biggest noticeable performance boost.

MAS Performance HEI Distributor & Wiring Set Including 65K Coil Compatible with Jeep AMC SBC/BBC V8 290 304 343 360 390 401 (Red HEI Kit) 5.0L 5.6L 6.4L

The MAS Performance HEI kit takes the ignition upgrade a step further by including a powerful 65K coil, capable of generating high voltage needed for performance applications. This distributor is CNC Machined, featuring a polished aluminum shaft and a chrome moly gear for long-term durability and precise timing. The bundled spark plug wires and pigtail wire harness make installation straightforward, turning a complex ignition swap into a bolt-on job. This is an excellent solution for AMC owners looking to maximize spark energy on a modified engine.

Key features that stand out:
* Includes a powerful 65,000V coil for a stronger spark.
* CNC Machined aluminum shaft and chrome moly gear for precision.
* High-quality brass terminals and protective plastic dust cover.

Pros:
– Exceptional spark energy for high RPM performance
– Complete kit simplifies the HEI conversion process
– High quality internal components enhance reliability

Cons:
– Overkill for a purely stock engine, where a simpler system might suffice.

Best for:
AMC 304 engines that have performance camshafts, headers, or higher compression ratios, demanding maximum spark energy.

Expert Opinion: The 65K coil is a crucial differentiator. If you’re trying to squeeze every bit of power out of your AMC 304, this component ensures the best spark plugs for amc 304 receive maximum voltage.

BDFHYK 6578 Iridium Spark Plugs Compatible with Cherokee 300 Special Calais Suburban Dart 2.0L 3.2L 5.0L L4 L6 V8 Replacement for BPR4ES Set of 8

For those seeking the pinnacle of durability and performance, these Iridium spark plugs are an outstanding choice. Iridium electrodes are extremely fine, allowing for superior ignition performance, a faster and more sensitive ignition jump, and significantly longer lifespan compared to copper. Made by a TS16949 certified manufacturer, these plugs are built to OE standards for durability. While the fitment list is broad, confirming the 6578/BPR4ES cross-reference for the AMC 304 (5.0L V8) confirms their compatibility and potential for increased power performance and saving energy consumption.

Key features that stand out:
* Extremely fine Iridium electrodes for superior ignition performance.
* OE standard performance and durability (TS16949 certified).
* Made from isostatic ceramics for high density and strength.

Pros:
– Exceptional lifespan (up to 4x copper)
– Improved fuel economy and power performance
– Faster and more sensitive ignition

Cons:
– Higher upfront cost compared to standard V-Power plugs.

Best for:
Drivers who prioritize maximum efficiency, longevity, and want the best possible material technology in their best spark plugs for amc 304.

Expert Opinion: Iridium is the way to go if you hate changing plugs. They maintain a precise gap and deliver excellent performance throughout their service life.

NGK V-Power Spark Plug WR5 (8 Pack) Compatible With FORD MUSTANG 1968-1973 5.0L/302

Though this product is explicitly listed for the Ford 302 (5.0L), it demonstrates NGK’s continued commitment to classic V8 engines. The WR5 heat range might be relevant to some AMC 304 users depending on their specific modifications or required temperature profile. Like all V-Power plugs, they are highly durable against electrical wear and feature that reliable construction. We include this to show that heat range considerations—even cross-referencing similar 5.0L V8s—are sometimes necessary when dealing with modified engines that require a slightly colder or hotter plug than stock.

Key features that stand out:
* High durability against electrical wear.
* NGK V-Power construction for improved fuel economy.
* Original equipment manufacturer approved quality.

Pros:
– Proven NGK quality and construction
– A useful option for cross-referencing heat ranges on high-compression setups

Cons:
– Requires careful verification against specific AMC 304 heat range requirements.

Best for:
Modified AMC 304 owners who have performed research and determined that the WR5 heat range aligns with their specific engine tuning needs.

Expert Opinion: Always confirm the correct heat range for your specific AMC 304 build. While copper plugs offer great conductivity, using the wrong heat range will lead to pre-ignition or fouling.

ACCEL 8198 Performance U-Groove Header Spark Plug – Pack of 8

The ACCEL 8198 plugs are designed specifically with performance in mind, particularly for engines running headers where space is tight—a common issue with the AMC V8. These plugs are often called “shorty” plugs, which are ideal for use in cramped spaces. Utilizing a U-Groove design, they aim to deliver significantly more power at high RPMs, offering instant throttle response and better fuel economy than standard plugs. They minimize fouling and flame dissipation, ensuring the spark remains consistent under load.

Key features that stand out:
* Ideal for use in cramped spaces (Shorty design).
* Deliver significantly more power at high RPM.
* U-Groove technology minimizes misfire and fouling.

Pros:
– Solves clearance issues around headers and manifolds
– Noticeable improvement in throttle response
– Designed for robust performance under demanding conditions

Cons:
– The shorter design may require specific plug wire boot types for optimal fitment.

Best for:
AMC 304 engines with performance headers or tight clearance issues, where standard plug length is problematic.

Expert Opinion: If clearance is your main challenge, these are the best spark plugs for amc 304 you can choose. The performance benefits are a bonus, but the primary utility is fitment.

Comparison Insights: Choosing the Right Ignition Strategy

When selecting the best spark plugs for amc 304, your decision should align with your engine’s current state—stock, mildly modified, or fully built.

For stock engines, the NGK V-Power plugs (GR4 or CJ5 specific) offer the best balance of reliability, cost, and proven performance. They are copper, meaning they conduct electricity exceptionally well, crucial for the AMC’s older ignition system.

If you hate routine maintenance, the BDFHYK Iridium plugs are the clear winner. Iridium offers the best longevity and maintains a consistent, powerful spark over tens of thousands of miles, although the upfront cost is higher.

Crucially, modern ignition components significantly enhance plug performance. If your 304 is still running points, upgrading to a complete HEI kit (like the 6512R or MAS Performance) paired with 8.0mm RLP Silicone Wires is perhaps the biggest improvement you can make. The HEI delivers a hotter spark that copper or iridium plugs can utilize fully.

Finally, if you have performance headers installed, ACCEL’s U-Groove Shorty plugs solve the physical clearance issues while still offering performance benefits at higher RPMs.

Final Verdict

Deciding on the best spark plugs for amc 304 requires honesty about your engine’s needs.

For the Classic Daily Driver: Go with the NGK V-Power Spark Plug GR4 (8 Pack). They are affordable, proven, and incredibly reliable for stock compression and general use. If you want maximum hassle-free mileage, splurge on the Iridium set.

For the Performance Build or Ignition Overhaul: The best strategy involves combining high-output voltage with high-efficiency plugs. We recommend the MAS Performance HEI Distributor & Wiring Set to provide maximum spark energy, paired with the BDFHYK 6578 Iridium Spark Plugs for unmatched ignition consistency and longevity under load.

FAQs About Best Spark Plugs for AMC 304

Q1: What is the correct spark plug gap for a stock AMC 304 V8 engine?

A stock AMC 304 typically requires a gap of 0.035 inches if you are running the original factory ignition system (points or low-output electronic ignition). However, if you upgrade to a high-output HEI distributor (like the MAS or 6512R kits mentioned), you can usually open the gap up to 0.045 inches or even 0.050 inches to take advantage of the hotter, stronger spark. Always verify the gap requirement recommended by your chosen spark plug manufacturer and ignition system vendor.

Q2: Why are spark plug wires listed alongside the best spark plugs for amc 304?

Spark plug wires are integral to the ignition system. An old or poor-quality wire set can lose significant voltage or introduce electrical resistance, negating the benefits of high-quality plugs (like Iridium or NGK V-Power). For performance or HEI systems, 8.0mm silicone wires (like the RLP sets) are necessary to handle the higher voltage and suppress radio frequency interference (RFI).

Q3: Should I choose copper, platinum, or iridium best spark plugs for amc 304?

Copper plugs (like NGK V-Power) are the best conductors and are great for stock or high-performance AMC engines, but they wear quickly. Platinum is a step up in lifespan. Iridium, however, offers the longest lifespan and features the finest electrode tip for the most focused, consistent spark. If longevity is critical, choose Iridium; if conductivity and cost are primary, stick with Copper.

Q4: How do I know if my AMC 304 needs new spark plugs?

Common signs that you need to change your best spark plugs for amc 304 include difficult starting, a rough idle, engine misfires (especially under load), and noticeable drops in fuel economy or acceleration. If you are running copper plugs, they should typically be inspected or replaced every 10,000 to 15,000 miles in an older V8.

Q5: What is the benefit of using “Shorty” plugs like the ACCEL 8198?

The primary benefit of “shorty” plugs is addressing physical clearance issues. Many classic AMC V8 engines, especially those with custom headers or modified exhaust manifolds, have very little space around the spark plug boots. The shorter design allows for easier installation and prevents the plug or wire boot from rubbing against hot components.

Q6: Does the spark plug heat range matter on a modified AMC 304?

Yes, the heat range is crucial. A plug that is too “cold” (dissipates heat too quickly) can foul out, especially during low-speed driving. A plug that is too “hot” (retains too much heat) can cause pre-ignition or detonation in high-compression or turbocharged engines, severely damaging the motor. Always choose a heat range appropriate for your engine’s compression ratio and operational temperature to ensure the best spark plugs for amc 304 deliver optimal performance.