Reinforced head gasket Subaru 2.2 EJ22E and 2.5 EJ25D

The Subaru engines covered

The EJ22E (2.2 litres) and the EJ25D (2.5 litres), both with sixteen valves, and the EJ22T, the turbocharged 2.2 litre version, are petrol flat-four engines fitted to the Subaru Impreza, Legacy, Outback and Forester listed in the compatibility table below. Each has two cylinder heads and therefore takes two gaskets.

The original gasket carries part number 11044-AA110 on the EJ22E, 11044-AA280 on the EJ22T and 11044-AA521 on the EJ25D. Subaru publishes neither its bore, nor its thickness, nor its construction. Sized for standard combustion pressure, it reaches its limit as soon as that pressure rises: clamping load drops, the head lifts and coolant finds its way into a cylinder.

Reinforced cylinder head gaskets

The gasket's hold also depends on the fasteners that clamp the head onto the block. A composite gasket is permanently crushed beyond 100 N/mm²; the 301 stainless steel of an MLS gasket withstands 517 N/mm², 5 times more, and returns to shape at every combustion. Replace any head bolt that is stretched or damaged.

This page presents part number C14084-051 from Cometic, the American maker of racing gaskets, in a single construction: the multi-layer steel MLS. Its bore is 100 mm and its thickness 1.3 mm. As a rule, the gasket bore chosen is at least 0.5 mm larger than the actual cylinder bore. It is sold individually: plan on two gaskets per engine.

Technical specifications

A gasket's volume is the free space it leaves above each cylinder. It adds to the combustion chamber and lowers the compression ratio: the thicker the gasket, the larger that volume. Here the single part number has a 100 mm bore.

Preparation and fitting

Before refitting, check the flatness of head and block with a straight edge and have the faces ground if necessary. The Cometic gasket comes pre-coated: do not apply any sealant.

Technical guide

The construction offered

Cometic MLS A stack of stamped and riveted stainless steel sheets. The outer sheets carry active beads that surround every cylinder and every fluid passage. Moderate clamping is enough to seal and the bore stays stable: a versatile construction, from the tuned naturally aspirated engine to moderate boost. The part number C14084-051 on this page is offered in this construction.

Choosing bore and thickness

Gasket bore. The Cometic MLS C14084-051 comes in 100 mm, in that bore only.

Thickness. No thickness is published for the original gaskets 11044-AA110, 11044-AA280 and 11044-AA521. A thicker gasket enlarges the combustion chamber and lowers the compression ratio; a thinner one reduces it and raises the ratio.

As the original thickness is not published, use a dial gauge to measure how far the pistons stand above the block's gasket face, especially if the removed gasket is thicker than 1.3 mm: this reading gives the clearance left between piston and head.

The brand

Cometic Gasket, Inc. is an American company created in 1989 and based in Concord, Ohio, specialised in engine gaskets and sealing solutions. It made its name with the custom gasket, made to the bore and thickness required and manufactured in the United States.

Advantages over the original gasket

When a reinforced gasket becomes necessary

• Adding forced induction, or raising boost on an already turbocharged engine
• Cylinder rebored beyond what the bore of the original gaskets, which Subaru does not publish covers
• Looking for a compression ratio different from standard, higher or lower
• Engine that has already lost its gasket, or is consuming coolant
• Competition use, where the gasket goes through repeated temperature rises

Vehicle compatibility

OEM part number: 11044-AA110 (EJ22E), 11044-AA280 (EJ22T) and 11044-AA521 (EJ25D).

Important: the part number on this page only suits the EJ22E, EJ22T and EJ25D engines: check the engine code of your Subaru before ordering.

Why switch to a reinforced gasket?

When the original gasket reaches its limit, the reinforced one takes over: under stronger combustion pressure it keeps its shape instead of crushing.

Fitting a bigger turbo, raising boost pressure or increasing the compression ratio puts the head gasket under strain first, as the weak link of the top end. A reinforced gasket prevents the leak, and with it a head removal far more expensive than the part itself.