The best head gaskets for your build are multi-layer steel (MLS) gaskets with the correct bore size and thickness for your engine. Match the gasket bore to your cylinder bore — or slightly larger for built engines — and choose thickness based on compression goals. For boosted and high-compression builds, MLS gaskets from proven brands like Cometic and Tomei are the industry standard.
Head gaskets seal the combustion chamber between the cylinder head and the block, taking the full force of combustion pressure. Stock-style composite gaskets work for mild builds, but boosted engines need multi-layer steel construction to handle elevated cylinder pressures and heat cycles. Thickness is a tuning tool: thinner raises compression, thicker lowers it and adds margin on turbo setups. Cometic offers application-specific bore sizes for EJ20, EJ25, FA20, 4G63, BP, and more.
Verify three things when ordering: bore size relative to your pistons, compressed thickness, and the correct engine application. Head gasket replacement is labor-intensive — heads come off and surfaces must be checked — so many builders replace head studs, timing components, and seals at the same time.
Popular brands include Cometic and Tomei. Popular picks include the Cometic 100mm bore head gasket for EJ25 WRX/STI models and the Cometic 93mm bore head gasket for 2002-2005 WRX EJ20. Browse related engine categories like performance valves, JE Pistons, and oil system parts, or the engine dressing collection for finishing details. For peace of mind on big jobs, read our warranties on aftermarket parts.
Can I reuse my old head gaskets?
No — head gaskets are single-use. Once torqued and heat-cycled, they take a permanent set. Always install new gaskets and new head bolts or studs.
Do I need a thicker head gasket for a turbo build?
Not necessarily. Thickness is a tuning tool: thinner raises compression, thicker lowers it. Most turbo builds pick a gasket thickness that hits a target compression ratio with their pistons.
How hard is it to install head gaskets?
It's an advanced job — the cylinder heads come off, surfaces must be checked for flatness, and bolts or studs must be torqued in the correct sequence. Many owners have a shop do it.
Which bore size do I need?
Match the gasket bore to your cylinder bore, or go slightly larger — never smaller. Check your year and model in the listing before ordering.
