NGK Spark Plug Stock # 4629

The NGK Spark Plug Stock # 4629 (C7HSA) is a proven, OEM-equivalent ignition component engineered for consistent combustion performance across a wide range of standard and lightly modified engines. Whether you're restoring a classic carburetor-fed cruiser, maintaining a daily driver, or tuning a weekend warrior, this spark plug delivers reliable cold-start characteristics and stable idle quality that mechanics have trusted for decades. NGK's reputation in performance and reliability makes this plug a smart choice for anyone serious about engine longevity and dependable ignition.

The C7HSA features a ceramic insulator body designed to handle standard-duty heat ranges without fouling under moderate load, making it ideal for carbureted and early fuel-injected platforms. The center electrode and ground strap geometry promote efficient spark initiation and steady flame-front propagation, crucial for maintaining timing stability across the RPM band. NGK's proprietary firing-end construction resists carbon buildup and electrode erosion, preserving gap integrity across thousands of miles—a key factor in avoiding lean misfires or rich stumbles common in aging ignition systems.

This plug works best in stock or mildly modified naturally aspirated engines where boost or nitrous oxide is not a consideration; if you're running forced induction, step up to a colder range. Installation is straightforward—simply gap to manufacturer spec (typically 0.028"–0.035" depending on application), thread by hand to avoid cross-threading, and torque with a spark-plug socket to prevent ceramic cracking. Always verify your vehicle's original equipment plug type in the owner's manual or service manual before purchase to ensure exact fitment and optimal engine response.