HKS SMG/K SET RB26DETT t=1.2

Race-Proven Head Sealing for High-Boost RB26DETT Builds

A high-output RB26DETT build does not tolerate head gasket failures. The HKS Stopper Type Metal Head Gasket Kit (23009-AN008) at 1.2mm thickness is engineered to hold the seal between block and head under the combustion pressures generated by modified Nissan Skyline GT-R engines, including race-level applications where boost and power density push conventional gaskets past their limits. This kit brings together the metal head gasket, exhaust manifold gaskets, intake manifold gaskets, and throttle body gaskets in a single, ready-to-install package.

Stopper Bead Technology for Maximum Combustion Sealing

The 23009-AN008 uses HKS's stopper-type construction, which forms a high-pressure sealing ring around each combustion chamber bore using a raised step (stopper) machined into the gasket plate. This approach concentrates clamping load precisely where combustion gas pressure is highest. The independent bead design adopted from HKS's proven 4G63 gasket provides each water hole and head bolt hole with its own isolated sealing bead, meaning that even if combustion gas bypasses one zone, overheat risk is reduced because the water passages remain independently sealed. HKS redesigned the stopper and bead geometry specifically for the RB26DETT, verified against a bench test vehicle producing 660ps and a circuit vehicle producing 600ps with 80kgm of torque. The 1.2mm thickness yields a compression ratio of approximately 8.7:1 with standard bore pistons and is compatible with both 86mm and 87mm pistons on the RB26DETT (independent water holes configuration). MPN 23009-AN008 covers both standard and slightly over-bored applications up to 87.5mm effective bore.

Key Features

• Stopper-type multi-layer metal construction for high-pressure combustion sealing
• 1.2mm thickness; bore diameter 87.5mm; compression ratio approximately 8.7:1 with standard pistons
• Independent water hole bead design limits overheat risk even if combustion gas leaks
• Compatible with 86mm and 87mm piston bores (independent water holes version)
• Kit includes exhaust manifold gaskets, intake manifold gaskets, and throttle body gaskets for full top-end service
• Race-proven: tested at 660ps on bench and 600ps / 80kgm in circuit driving
• Fits RB26DETT in BNR32, BCNR33, and BNR34 (Nissan Skyline GT-R R32, R33, R34)
• HKS recommends use with reinforced head bolts for maximum clamping force
• MPN: 23009-AN008 | HKS Part: 23009-AN008 | Reference: 23009-AN008

What's Included

• 1x HKS Stopper Type Metal Head Gasket (23009-AN008, t=1.2mm, 87.5mm bore)
• 2x Exhaust manifold gaskets (metal bead type)
• 1x Intake manifold gasket (metal bead type)
• 6x Throttle body gaskets (metal bead type, one per individual throttle body on the RB26DETT)

Note: Head bolts are not included. HKS recommends replacing head bolts with reinforced units when installing this gasket in high-performance applications.

Technical Specifications

Installation Instructions

1. Drain the engine coolant and engine oil fully before disassembly. Remove the intake manifold, exhaust manifolds, and all accessories mounted to the cylinder head.
2. Loosen and remove the cylinder head bolts in reverse torque order (outside in) per the Nissan factory service manual. Lift the cylinder head clear of the block.
3. Remove all remnants of the old head gasket from both the block deck surface and the cylinder head mating surface. Use a plastic or aluminum scraper to avoid scoring the aluminum head. Inspect both surfaces for warping with a precision straightedge; maximum allowable warpage is 0.03mm.
4. Clean both surfaces thoroughly with brake cleaner or equivalent. Ensure all coolant and oil passages are clear.
5. Position the HKS 23009-AN008 head gasket on the block deck with the correct side facing up (confirm orientation per the included markings). Align to the dowel pins.
6. Lower the cylinder head onto the gasket. Hand-thread new or inspected head bolts. HKS recommends replacing head bolts with reinforced units for modified RB26 applications.
7. Torque head bolts in sequence (center out) in multiple passes: first pass 30 N-m, second pass 60 N-m, third pass to final specification per the factory service manual (typically 90 N-m or angle-torque method). Refer to HKS reinforced head bolt instructions if applicable.
8. Install the exhaust manifold gaskets and manifolds using the included gaskets. Torque manifold bolts to factory specification.
9. Install the intake manifold using the included intake manifold gasket. Install throttle bodies using the included throttle body gaskets (6 pieces for the individual throttle body arrangement).
10. Refill coolant and oil. Start the engine and bring to operating temperature. Re-torque head bolts if required by the head bolt manufacturer's procedure. Check for leaks before returning to high-boost operation.

Frequently Asked Questions

What is the compression ratio with this gasket on a stock-bore RB26DETT?
With a standard 86mm bore and stock pistons, the HKS 23009-AN008 at 1.2mm thickness yields a compression ratio of approximately 8.7:1. With an 87mm overbore piston, the ratio will be slightly higher due to increased swept volume.

Does this gasket work with 2.8L stroker builds?
Yes, provided the piston bore is within the 86 to 87mm range for which the independent water holes version is designed. HKS's own 2.8L complete engine documentation references the 1.2mm stopper-type gasket (this category) as standard equipment on the RB26 2.8L High Response build.

What head bolts does HKS recommend with this gasket?
HKS recommends replacing factory head bolts with HKS reinforced head bolts when installing this gasket in high-performance applications. Stock head bolts are stretch-to-yield fasteners and should not be reused after removal.

Is a special surface finish required on the block deck and cylinder head?
Yes. Metal head gaskets are more sensitive to surface finish than composite gaskets. HKS recommends a surface finish of Ra 1.6 micrometers (approximately 60 RMS) or better on both the block deck and the cylinder head mating surface for optimal sealing.

Can I use this gasket with the HKS 22001-AN001 upgraded valve springs?
Yes. The 23009-AN008 and 22001-AN001 are both components of the HKS Step 2 engine build system. They are routinely used together in the same engine assembly and appear together in HKS's published 2.8L engine build specifications.

Does the kit include stem seals or head bolts?
No. The kit includes the metal head gasket, exhaust manifold gaskets, intake manifold gaskets, and throttle body gaskets only. Stem seals (22999-AN004), head bolts, and other fasteners are sold separately.

Will this gasket fit R32 GT-R models from 1989 onward?
Yes. The 23009-AN008 fits all RB26DETT applications in the BNR32 (1989 to 1994), BCNR33 (1995 to 1998), and BNR34 (1999 to 2002). All three generations share the same RB26DETT engine architecture and head bolt pattern.

What is the difference between stopper type and grommet type head gaskets?
Stopper type gaskets (like 23009-AN008) use a raised metal stop ring around the combustion bore to create high sealing pressure and allow for a thinner gasket plate layer in the stopper zone. Grommet type gaskets use a wire ring pressed into a groove in the gasket to seal the combustion chamber. Stopper type gaskets are generally preferred for race and high-boost applications due to their resistance to combustion gas blow-through.

WARNING: This product can expose you to chemicals including steel and metalworking compound residues, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information, visit www.p65warnings.ca.gov.