HKS Super Fire Racing M40i Iridium Spark Plug (NGK 8, ISO) - 10 Pack

The HKS Super Fire Racing M40i is an ISO-type iridium spark plug with an NGK 8 equivalent heat range, for tuned and stock performance engines. Its 0.6 mm iridium center electrode and platinum-chip outer electrode lower the required firing voltage for strong ignition under high boost or lean conditions, while the thermal edge and spark-support gap resist carbon fouling. The ISO seat fits a wide range of Japanese turbo and naturally aspirated engines (RB, SR, VG, and similar) calling for an ISO φ14 plug. Sold as a 10-pack (wholesale case); a typical engine needs one plug per cylinder.

Specifications

Shipping

• In-stock orders placed before 3 PM EST ship the same day — everything else ships within 24 hours.
• Standard, expedited, and overnight options at checkout.
• Oversized items ship by freight and take longer.
• Backordered items ship as soon as stock lands — contact us for lead times.
• International orders: prices do not include VAT, duties, or import fees. Your country charges these at import and they are the buyer’s responsibility.

Returns

• 30-day returns on new, uninstalled items in original packaging with all hardware.
• Standard returns: 8% restocking fee, buyer pays return shipping. Both waived if the item is defective or we made the error.
• Installed or used parts can’t be returned — confirm fitment before you install.
• Special orders and custom items are final sale.
• Email us for return authorization before shipping anything back.

Full details: Shipping Policy · Refund Policy