Denso 6021 Spark Plug

Denso 6021 U-Groove Spark Plug

Denso 6021 is a conventional spark plug built for older ignition systems that need reliable secondary ignition performance. Its U-Groove electrode design helps improve ignitability, supporting smoother combustion and more consistent engine efficiency in a wide range of classic Chrysler, Chevrolet, Pontiac, Oldsmobile, Buick, Cadillac, and Dodge applications.

Key Features

• U-Groove ground electrode design for improved spark exposure
• Copper center electrode core for dependable heat transfer
• Nickel center and ground electrode tip materials
• 5000 ohm resistor for ignition noise suppression
• 0.7 pre-gap size for factory-style setup
• 14 mm thread diameter, 9.50 mm reach, flat seat
• 20.6 mm hex size and manufacturer heat range 14
• Cross-reference: DENSO Auto Parts W14PR-U

Product Details

This Denso U-Groove Conventional spark plug is engineered around the brand’s U-Groove electrode profile, which increases the spark’s exposure area at the gap. That design supports more reliable ignition in engines where consistent firing matters, especially in older carbureted and distributor-based systems. The Denso 6021 is a practical OE-style replacement for vehicles such as the Chevrolet Camaro, Pontiac GTO, and Oldsmobile Cutlass, along with many other classic V8 applications listed in the fitment data.

Compatible With 1951-1978 Chrysler New Yorker, Chrysler Newport, Chrysler Town & Country, Chrysler 300, Chrysler Imperial, Dodge Magnum, Dodge Monaco; 1954-1967 Buick Skylark, Buick LeSabre, Buick Century, Buick Roadmaster; 1955-1967 Cadillac DeVille, Cadillac Eldorado, Cadillac Fleetwood; 1962-1970 Chevrolet Bel Air, Chevrolet Caprice, Chevrolet Camaro, Chevrolet Corvette, Chevrolet Impala, Chevrolet Malibu, Chevrolet El Camino, Chevrolet Blazer, Chevrolet C10 Suburban, Chevrolet C20 Suburban, Chevrolet K10 Suburban, Chevrolet K20 Suburban, Chevrolet Nova; 1960-1970 Pontiac Bonneville, Pontiac Catalina, Pontiac Firebird, Pontiac Grand Prix, Pontiac GTO, Pontiac LeMans, Pontiac Tempest; and 1964-1973 Oldsmobile Cutlass, Oldsmobile Cutlass Supreme, Oldsmobile Delta 88, Oldsmobile 98, Oldsmobile Starfire, Oldsmobile Toronado, Oldsmobile Omega, Oldsmobile Custom Cruiser.

What It Helps Address

• Hard starting caused by worn or inconsistent spark plugs
• Misfire concerns from weak ignition at the plug gap
• Rough idle in older engines with conventional ignition systems
• Reduced combustion efficiency from aged secondary ignition components
• Ignition noise issues in resistor-equipped applications

Installation Notes and Tips

Verify thread diameter, reach, seat type, and heat range against the vehicle’s original specification before installation. The pre-gap size is listed at 0.7, but final gap should always be checked and adjusted to the engine manufacturer’s specification. Use proper torque procedures for flat-seat spark plugs and inspect plug wires, distributor components, and ignition timing when replacing plugs on classic vehicles.

Quality Assurance

Denso is known for ignition components used in OE and service applications, and the 6021 follows a conventional spark plug design with nickel and copper materials selected for dependable operation in the listed vehicles. Part number 6021 is also referenced as DENSO Auto Parts W14PR-U.