Best Spark Plugs For 400 Small Block Chevy

#1 · Best Overall

1. ACDelco R45TS 8-Pack

• Core Material: Copper
• Top Material Type: Ceramic
• Compatible with Vehicle Type: Car
• Thread Size: 14

Best for: Marine-ready copper-core replacement.

Why it ranks #1: The R45TS designation, copper core, corrosion-resistant coatings, and eight-plug pack make this the clearest complete-set choice when specifications match.

A copper core gives the ACDelco R45TS thermal properties for heat transfer, while black onyx coating and nickel-chrome center-electrode sheathing help resist corrosion. The eight-plug package suits a full replacement set, and its stated marine availability makes it relevant to buyers maintaining a boat engine as well as a car.

Copper core construction supports heat transfer and plug durability, two practical priorities in a replacement spark plug. Corrosion protection comes from two named features: black onyx coating and nickel-chrome alloy sheathing on the center electrode. With eight R45TS plugs included, the package provides a full set for an eight-cylinder setup. A 14 mm thread is specified, but the listing does not establish every 400 small-block configuration; check the engine’s required plug details before installation.

Skip it if you need a stated plug gap to guide setup; NGK UR5 lists a 0.040-inch gap.

This package suits buyers seeking eight ACDelco R45TS conventional plugs with copper-core heat transfer and corrosion protection, including marine users. Treat the stated 14 mm thread as one fit detail, not confirmation for every 400 small-block build.

Listed on Amazon as: R45ts Pkg 8

#2 · GM Replacement Set

2. 1A Auto R45TS Set

• Core Material: Copper
• Top Material Type: Metal
• Compatible with Vehicle Type: Car
• Thread Size: 14mm

Best for: GM OE-style replacement set.

Why it ranks #2: This eight-plug R45TS set is described as engineered and validated to GM specifications, and lists a 14 mm thread and 1.12 gap.

GM engineers design and validate this R45TS as an OE part for Chevrolet, Buick, GMC, and Cadillac vehicles, giving GM-focused buyers a specification-led replacement option. The set contains eight copper-core plugs, and the supplied description connects their ignition role to combustion and proper timing across city, commute, and highway driving.

The OE design and validation for named GM vehicle makes make this set particularly relevant to buyers maintaining a compatible GM application. Copper core construction supports heat transfer, while the description explains that the plug works with the ignition coil to create the spark for combustion. Eight plugs provide a set quantity for a full replacement, and the listed 1.12 gap is a specific setup detail to consider alongside engine requirements.

Skip it if you require a listed 0.040-inch gap; NGK UR5 specifies that measurement.

This is a reasonable choice for a buyer seeking an R45TS-style, eight-plug GM replacement for compatible Chevrolet or related GM vehicles. The listed gap is 1.12, so make sure that specification aligns with the intended 400 small-block setup.

Listed on Amazon as: AC Delco R45TS Spark Plug Set of 8 for Chevy GMC Buick Cadillac Pontiac Olds

#3

3. ACDelco R45TS Single

• Core Material: Copper
• Top Material Type: Nickel
• Compatible with Vehicle Type: UTV
• Thread Size: 14mm

Best for: Single R45TS OE replacement.

Why it ranks #3: It offers the R45TS designation, copper core, nickel-chrome electrode sheathing, and a ribbed suppressor seal, but the listing is for one plug.

ACDelco’s GM Original Equipment R45TS pairs a copper core with black onyx coating and nickel-chrome center-electrode sheathing, combining heat-transfer and corrosion-related features in one conventional plug. Its ribbed suppressor seal is also specified to help prevent flash-over and misfires, while marine use is listed as an option.

The copper core supports heat transfer and plug durability, while black onyx coating and nickel-chrome alloy sheathing help reduce corrosion in different areas of the plug. A ribbed suppressor seal extends resistance to help prevent flash-over and misfires, a practical ignition-related benefit. The listing identifies an R45TS with a 14 mm thread and marine availability. Confirm that the R45TS specification suits the particular engine before choosing this replacement plug.

Skip it if you want a full set in one purchase; ACDelco R45TS Pkg 8 supplies eight plugs.

This single R45TS suits a buyer replacing an individual compatible plug and prioritizing copper-core construction, corrosion protection, and suppressor-seal features. It is not an eight-plug package, and engine-specific fit still depends on the required specification.

Listed on Amazon as: ACDelco GM Original Equipment R45TS (19354415) Conventional Spark Plug

#4 · Marine-Use Set

4. ACDelco R44T 8-Pack

• Core Material: Copper
• Top Material Type: Nickel
• Compatible with Vehicle Type: Watercraft
• Thread Size: 14mm

Best for: Marine use with flashover resistance.

Why it ranks #4: This eight-pack has a copper core, 14 mm thread, anti-corrosion electrode sheathing, and stated availability for marine applications.

A ribbed suppressor seal is the defining feature of this ACDelco R44T, extending resistance to help prevent spark flash-over and misfire. Its copper core supports heat transfer and plug durability, while nickel-chrome sheathing helps protect the center electrode. The pack of eight is listed for marine applications.

The ribbed suppressor seal addresses spark flash-over and misfire, making it a relevant feature for buyers focused on dependable ignition behavior. Copper core thermal properties support heat transfer and durability, while nickel-chrome alloy sheathing helps prevent corrosion on the center electrode. Eight plugs are supplied, and the stated 14 mm thread is useful when checking application details. Its marine availability is explicit; this listing does not give a gap specification for installation.

Skip it if you need a listed gap for setup; NGK UR5 specifies 0.040 inch.

Choose this eight-pack if the R44T specification suits your engine and marine use is relevant. Its suppressor seal and corrosion-conscious materials are practical features, but buyers who need a stated gap will find that detail elsewhere.

Listed on Amazon as: ACDelco R44T Professional Conventional Spark Plug (Pack of 8)

#5

5. ACDelco CR43TS 8-Pack

• Core Material: Copper
• Top Material Type: Nickel
• Compatible with Vehicle Type: Car
• Thread Size: M14

Best for: Eight-pack with suppressor seal.

Why it ranks #5: The eight-plug copper-core set adds a ribbed suppressor seal and black onyx coating, though its CR43TS designation differs from the R45TS options.

A ribbed suppressor seal is the practical highlight of ACDelco’s CR43TS eight-pack, extending resistance to help prevent spark flash-over and misfire. Copper-core thermal properties support heat transfer and durability, while black onyx coating helps prevent corrosion. The listing also identifies marine use, giving this conventional plug more than one stated application context.

The ribbed suppressor seal targets flash-over and misfire, while the copper core supports heat transfer and plug durability. Black onyx coating adds a corrosion-prevention feature, which complements the listed marine availability. Eight plugs come in the box, a useful quantity for a full set where the CR43TS specification fits. The thread is listed as M14; that detail should be considered along with the engine’s required plug specification before installation.

Skip it if you need a stated gap before installation; NGK UR5 lists 0.040 inch.

This package suits buyers who want eight ACDelco CR43TS plugs with a suppressor seal and corrosion-conscious construction, including marine users. Check that the CR43TS and M14 thread details match the intended 400 small-block application.

Listed on Amazon as: ACDelco CR43TS 5614029 (05614029) Professional Conventional Spark Plug BOX OF 8

#6 · Header-Clearance Design

6. NGK UR5 V-Power

• Core Material: Nickel
• Top Material Type: Nickel
• Compatible with Vehicle Type: Car, Truck
• Thread Size: RM

Best for: NGK UR5 eight-plug set.

Why it ranks #6: The eight NGK UR5 plugs list a 0.040-inch gap and nickel core; the listed short name and gap still require fitment verification.

NGK’s UR5 set supplies eight V-Power spark plugs with a stated 0.040-inch gap, offering buyers a concrete setup specification alongside a named replacement part. Its nickel core and car-and-truck vehicle compatibility make it an option to investigate for a 400 small-block, while the listing directs buyers to check application guidance.

The 0.040-inch gap gives a buyer a precise figure to compare with the engine’s required setup before installation. The eight-piece quantity can cover a full set, and the UR5 model designation makes the plug identity clear for application research. Nickel is listed as both core and top material. NGK advises consulting the owner’s manual and compatibility list, so this product’s useful fit details still need to be matched to the specific engine.

Skip it if you want copper-core plugs with corrosion features specified; NGK YR5 lists copper core and trivalent plating.

Consider this set if the UR5 application and 0.040-inch gap match your engine requirements and you want eight plugs together. NGK specifically recommends checking the owner’s manual and compatibility list before installation.

Listed on Amazon as: Set (8pcs) NGK V-Power Spark Plugs Stock 2771 Nickel Core Tip Standard 0.040in UR5

#7 · Shorty Plug

7. ACCEL 8199 Shorty

• Core Material: Copper
• Top Material Type: Alloy Steel
• Compatible with Vehicle Type: Motorcycle
• Thread Size: 14 mm

Best for: Tight header-clearance installations.

Why it ranks #7: Its shorter overall length is specifically intended to improve clearance and access around tubular headers, with a copper-core center electrode.

ACCEL’s shorty profile is the central reason to consider the 8199: its shorter overall length than OE-style plugs can help create clearance around tubular exhaust headers. The listing also says the design improves socket or wrench access in cramped spaces, addressing installation and removal where standard-length plugs are difficult to reach.

The shorty form is intended for tubular-header clearance, helping avoid header dimpling where space is tight. ACCEL also says the shorter overall length improves access for a socket or wrench, which can make installation and removal more manageable in cramped areas. A copper-core center electrode and projected tip are specified, with the product description connecting shorty plugs to reducing burned plug boots. Thread size is listed as 14 mm.

Skip it if you have ample header clearance and want an OE-style length; ACDelco R45TS is a conventional plug.

Choose the ACCEL 8199 when headers crowd plug boots or tool access, and its shorty dimensions address that installation constraint. Buyers without a clearance problem should weigh the shorty-specific purpose and confirm the plug suits their engine.

Listed on Amazon as: ACCEL 8199 HP Copper Spark Plug – Shorty

#8

8. NGK YR5 8-Pack

• Core Material: Copper
• Top Material Type: Metal, Nickel
• Compatible with Vehicle Type: Car, Truck
• Thread Size: 14 millimeters

Best for: Small-block Chevy stock replacement.

Why it ranks #8: This copper-core eight-pack is listed for a 350 Chevy small-block application, not a 400, so verify compatibility before considering it.

NGK identifies this YR5 eight-pack for a 5.7L/350 Chevy small-block Gen I application, making its stated engine family the key shopping detail. A copper core aids heat removal, and trivalent metal plating helps resist corrosion and seizing. The listing describes it as a stock-replacement series plug.

The named Chevy small-block Gen I family gives this plug useful application context for buyers comparing replacement parts, though the listed vehicle example is a 1972 5.7L/350 rather than a 400. Copper core construction aids heat removal, while the alumina silicate ceramic insulator is described as strong and supportive of heat transfer. Corrugated ribs help prevent flashover, and triple seals prevent leakage, adding several practical construction details to weigh.

Skip it if you require an explicitly listed 400 application; ACDelco R45TS is identified as a GM OE part.

This eight-pack suits buyers comparing NGK stock-replacement plugs for a Chevy small-block Gen I, especially the listed 5.7L/350 application. For a 400, treat that engine-specific example as a boundary and verify the required plug specification.

Listed on Amazon as: NGK Standard Series Spark Plug YR5 (8 Pack) for CHEVROLET CHEVELLE MALIBU 1972-1972 5.7L/350

#9

9. ACDelco Spark Plug

• Core Material: Copper
• Top Material Type: Nickel
• Compatible with Vehicle Type: Watercraft

Best for: Marine-use corrosion protection.

Why it ranks #9: The listing specifies copper core and corrosion-resistant features but provides no model designation, pack quantity, or thread size to confirm fit.

ACDelco specifies both black onyx coating and nickel-chrome alloy sheathing to help prevent corrosion, making protection the defining feature of this conventional spark plug. Its copper core supports heat transfer and durability, and the listing names marine use. The product information identifies it as an ACDelco plug without a model designation in the title.

The copper core provides thermal properties for heat transfer and increased plug durability, while black onyx coating helps prevent corrosion on the plug. Nickel-chrome alloy sheathing separately helps protect the center electrode, giving buyers two specified corrosion-related features to consider for marine use. The listing identifies a watercraft-compatible ACDelco plug and provides manufacturer part number 19300383. It does not name a model in the title, so buyers should use the supplied identity when checking their application.

Skip it if you want an R45TS model explicitly identified; ACDelco GM Original Equipment R45TS names that model.

This plug suits buyers seeking ACDelco copper-core construction and specified corrosion protection, including marine users. Because the title does not name a model, match manufacturer part number 19300383 against the exact requirement for the 400 small-block.

Listed on Amazon as: SPARK PLUG

#10

10. Champion Copper Plus 400

• Core Material: Copper
• Top Material Type: Metal
• Compatible with Vehicle Type: Car
• Thread Size: 14mm

Best for: Four-plug copper-core replacement.

Why it ranks #10: Despite the model number 400, the listing describes a small-engine plug and a four-pack, making it the least supported match for a 400 Chevy V8.

Champion’s copper-core center electrode provides conductivity and heat control, the key construction feature of this Copper Plus RV9YC plug. The package contains four plugs and is identified as an OE-type replacement, making the quantity an important consideration for a 400 small-block buyer planning a complete engine set.

Copper core construction supports conductivity and heat control, which Champion associates with good overall wear and longer plug life. The listing also identifies the RV9YC as an OE-type replacement and says the plug inhibits corrosion, giving buyers both replacement context and a material-protection detail. Four plugs come in the package, so a buyer planning a complete eight-cylinder set needs to account for the quantity. The product lists a 14 mm thread.

Skip it if you want eight plugs in one package; ACDelco R45TS is supplied as an eight-pack.

This Champion pack fits buyers seeking a copper-core, OE-type replacement and needing four plugs. For a complete 400 small-block set, factor in its four-piece quantity and verify that the RV9YC specification matches the intended engine.

Listed on Amazon as: Champion Copper Plus Small Engine 400 (RV9YC) Pack of 4 (UPC 037551130795) for 1970-1995 Chevrolet C10