Code No. 23001-AT004



0.5mm, 0.7mm, and 1.0mm thick bore stopper type metal head gaskets are available for the FA20 engine of 86 & BRZ.
This gasket provides higher bore sealing durability than stock.
Use with HKS Capacity Upgrade Kit or Supercharger Kit provides the optimum performance.



Compression Ratio

Piston Gasket thickness (mm) compression ratio
STOCK STOCK 0.6 12.5
HKS 0.5 12.6
HKS 0.7 12.4
HKS ※2 HKS 0.5 12.4
HKS 0.7 12.1
HKS 1.0 11.7
HKS ※3 HKS 0.5 11.1
HKS 0.7 10.9
HKS 1.0 10.5

※These are design calculation ratios.
※2 FA2. 2.1L KIT(21004-AT002)
※3 FA20 2.1L KIT Low Comp(21004-AT003)




<POINT-1> Maintain high seal with high power!
All three types are durable against the high engine output. Stopper structure of the bore seal is designed to be a separated type to prevent leakage even under high gas-pressure at high engine output.

<POINT-2> Contact surface pressure is improved!
Special coating was applied on the head and cylinder side to improve sealing performance when tightening the bolts.


With t=0.5mm gasket, NA engine’s compression ratio increases compared with the stock!
The durability of the bore seal of this gasket t=0.5mm for NA engine is improved, and the compression ratio increase compared with the stock that makes this gasket ideal for one-make race. (This gasket can be installed to a supercharged engine.)

t=0.7mm for Supercharged Engine
The t=0.7mm type utilizes a stopper taller than the t=0.5mm type to provide higher bore seal durability.  With a stock pistons, the compression ratio is reduced only by 0.1; it allows to maintain high heat efficiency.

t=1.0mm for HKS Capacity Upgrade Kit + Supercharger
Installing the t=1.0 type gasket to a vehicle with the supercharger enables to adjust the compression ratio of Capacity Upgrade Kit; setting range can be widened.





Engine Thickness (mm) Compression Ratio Bore Code No. Manual Remarks
FA20 1.0 ε=11.7 φ89.5 23001-AT004 For supercharger engine, LH/RH each, opposed bead stopper type