IAG Performance Fire-Lock Head Gasket Pair EJ25 / EJ257 100mm Bore .051 Inch Thickness For Use w/ 14mm Head Studs

The IAG proprietary Fire-Lock™ Head Gasket System has been proven in IAG’s record-setting race cars and is widely regarded as the strongest Subaru head gasket solution ever produced. Engineered specifically for extreme horsepower applications, the Fire-Lock™ system has been tested in engines producing in excess of 1,000 horsepower.

Unlike conventional head gasket designs, IAG engineers separated the critical functions of combustion chamber sealing and fluid sealing into two independent components. This approach dramatically improves reliability under extreme cylinder pressures commonly seen in high-boost EJ25 turbocharged engines.

The Fire-Lock™ system draws inspiration from proven diesel engine technology. Each cylinder bore features a precision-machined counterbore that accepts a specially sized alloy fire ring. When paired with the corresponding head gasket bore and compression shim, the fire ring creates a powerful mechanical seal once the cylinder heads are torqued in place. During manufacturing of the IAG 950 and 1150 Closed Deck Cases, a recessed groove is machined at the top of each cylinder to securely locate the Fire-Lock™ ring. Once installed, the ring stands proud above the deck surface, delivering exceptional combustion sealing that far exceeds traditional MLS gasket capabilities.

IAG Fire-Lock™ rings are manufactured from a proprietary alloy, held to extremely tight tolerances, and heat-treated to ensure consistent strength and durability under extreme thermal and pressure loads. Due to the sealing forces involved, 14mm head studs are required when using Fire-Lock™ head gaskets.

The gasket bodies themselves are constructed from an asbestos-free composite material and feature silicone-based beading in critical areas to ensure proper sealing of all oil and coolant passages. By isolating fluid sealing from combustion sealing, the system prevents coolant and oil intrusion into the cylinders while maintaining maximum clamp load at the combustion chamber.

The combination of precision alloy fire rings, composite gasket bodies, and high clamp force provided by 14mm head studs delivers unmatched sealing performance for high-horsepower Subaru EJ25 turbo engines. IAG 950 and 1150 Closed Deck Cases are machined specifically to accept Fire-Lock™ rings and 14mm head studs (not included) to ensure optimal sealing integrity.

Installation Notes:

• If a block or cylinder head was previously o-ringed the groove must be filled and resurfaced before using this type of gasket.
  
• These gaskets require IAG ARP 14mm head studs to achieve the required torque necessary for proper installation.
  
• Due to the required torque, any block that was previously honed will need to go to the next size overbore.
  
• Future servicing will require cylinder head resurfacing due to an imprint left from the Fire-Lock™ rings.