HKS Grommet Type Head Gasket FA24 t=0.8

Grommet Type Head Gasket for FA24, 0.8mm Thickness

The HKS Grommet Type Head Gasket for the FA24 at 0.8mm thickness is a performance head gasket option for the 2022+ Toyota GR86 and Subaru BRZ engine. The grommet type construction uses a fire ring around each cylinder bore that provides a more consistent and reliable combustion chamber seal under high-load conditions. The 0.8mm thickness is for applications where minimal compression ratio change is desired. The thinner gasket maintains the factory compression ratio more closely than thicker alternatives.

Specs & Highlights

• Grommet type head gasket construction
• 0.8mm thickness, minimal compression ratio change
• Fire ring bore sealing design
• FA24 specific fitment
• For performance builds and high-load applications
• Fitment: 2022+ Toyota GR86 / Subaru BRZ (FA24)

91.0mm Bore, 0.3mm Fire Ring Height, 0.8-1.6 Ra Surface Requirement

The t=0.8mm grommet gasket is the direct-fit option for standard FA24 deck height. Bore diameter is 91.0mm, matching the FA24's factory bore. The grommet construction uses a steel fire ring insert with a 0.3mm height above the gasket surface, which creates the combustion chamber sealing ring under head bolt clamping force. Surface finish requirement on the cylinder head and block deck is 0.8–1.6 Ra (μm), verify head surface condition before installation. Clamping torque specification follows the FA24 OEM head bolt sequence and value.

Grommet Construction vs Multi-Layer Steel

The grommet construction provides a sealing advantage over standard multi-layer steel gaskets in high-load situations. The fire ring creates a dedicated sealing surface around each cylinder bore that maintains its integrity under repeated thermal cycling and elevated combustion pressure. For FA24 builds running increased boost or high-compression naturally aspirated configurations, the grommet head gasket is the appropriate sealing solution.

t=0.8mm for Standard Deck Height and NA or Moderate Boost

The 0.8mm thickness is the standard specification for most FA24 performance builds that do not require compression ratio adjustment. If your build requires a specific compression ratio change. For example, with aftermarket pistons or head resurfacing, the 1.2mm version (AT005) is available for the additional thickness and corresponding compression reduction.

The FT Breakdown

The grommet head gasket is the head gasket for serious FA24 builds. It is a detail part with a real engineering basis. The fire ring construction works better under the conditions a performance FA24 creates than the OEM gasket design. Install it when you are in the engine and do it right. The 0.8–1.6 Ra surface finish requirement for the cylinder head and block deck is the detail most often overlooked during head gasket installations. A surface that is too rough tears the soft metal fire ring insert on initial clamping; a surface that is too smooth does not provide the micro-mechanical interlock the gasket needs for long-term sealing. Verify the machined surface finish specification before installing this gasket.