HKS 23001-AT004 Opposed Bead Stopper Type Metal Head Gasket 1.0mm FA20

The HKS 23001-AT004 is an Opposed Bead Stopper Type Metal Head Gasket engineered for the FA20 engine. Sold as a left/right pair (LH/RH), this set delivers significantly higher bore sealing durability compared to the OEM stock gasket, making it the ideal choice for high-output, boosted, and stroker engine builds.

At 1.0mm thickness (versus the stock 0.6mm), this gasket is specifically designed for use with the HKS Capacity Upgrade (Stroker) Kit or Supercharger Kit, providing a lower compression ratio of 11.7:1 compared to the stock 12.5:1. It is not intended for use with a stock, unmodified engine.

Key Features:

• Opposed Bead Stopper construction — utilizes a separated stopper structure around each combustion chamber bore to prevent leakage under extreme gas pressure and high engine output
• Multi-layer steel construction — multiple layers of high-grade, heat and corrosion-resistant steel maintain gasket integrity under severe high-horsepower and high-boost conditions
• Special fluorine rubber coating — applied to both the head and cylinder block sides to improve contact surface pressure and sealing performance during bolt torque-down
• 1.0mm thickness — lowers dynamic compression ratio for boosted and stroked applications requiring reduced compression
• 89.5mm bore diameter — engineered for the FA20 engine platform
• Complete set — includes both left (LH) and right (RH) gaskets for a full engine seal

Note: Compression ratios are design calculation estimates and actual ratios achieved may vary depending on application. HKS metal head gaskets are not designed to correct sealing issues caused by head or block surface irregularities.

HKS stopper-type gaskets represent the highest tier of the HKS metal head gasket lineup, incorporating the maximum number of steel plate layers combined with a molded stopper ring for superior sealing performance over bead or grommet-style alternatives. Built to handle the demands of serious performance engine builds, the 23001-AT004 is the low-compression option recommended for boosted FA20 applications paired with the HKS stroker or supercharger kits.