Reinforced cylinder head gasket Subaru Impreza Legacy Forester 2.0 EJ20

The Subaru engines covered

The EJ20 petrol engine, a 2.0 litre (1,994 cc) flat-four, powers the Subaru Impreza, Legacy and Forester listed in the compatibility table below.

The original gasket carries the part number 11044-AA360. Subaru publishes neither its bore, its thickness nor its construction. Designed for the standard combustion pressure, it reaches its limit as soon as that pressure rises: the clamping load fades, one head lifts slightly and coolant finds its way into a cylinder.

Reinforced cylinder head gaskets

Sealing does not rest on the head gasket alone: it also depends on the fasteners that clamp each head to the block. A composite gasket is permanently crushed beyond 100 N/mm²; the 301 stainless steel of the MLS withstands 517 N/mm², 5 times more, and recovers its shape at every combustion.

This page presents part numbers from the American maker Cometic, a specialist in competition gaskets, in a single construction: the MLS, in 93 mm bore, in 18 thicknesses from 0.69 to 3.56 mm. A flat engine has two cylinder heads, so two gaskets are needed.

Technical specifications

A gasket's volume is the free space it leaves above each cylinder. Added to the combustion chamber, it lowers the compression ratio; only gaskets of the same bore can be compared directly. All the gaskets on this page share the same 93 mm bore, so their volumes can be compared directly.

Preparation and fitting

Before assembly, check the gasket faces of each head and of the block with a straight edge, and have them resurfaced if necessary. Cometic gaskets come coated: do not apply any sealant.

Technical guide

The construction offered

Cometic MLS A stack of embossed stainless steel sheets held together by rivets. The outer sheets carry beads that surround each cylinder and each fluid passage: moderate clamping is enough to seal and the bore distorts little. The construction suits a tuned naturally aspirated engine as well as moderate boost.

Choosing bore and thickness

Gasket bore. The Cometic MLS is offered here in 93 mm (C4260), in 18 thicknesses.

Thickness. Subaru publishes no original thickness for this gasket. A thicker gasket enlarges the combustion chamber and lowers the compression ratio; a thinner one reduces it and raises the ratio.

With no original thickness published, use a dial gauge to measure how far each piston stands proud of the block's gasket face, especially if resurfacing is planned: this reading shows the clearance left between piston and head.

The brand

Cometic Gasket, Inc., founded in 1989 in Concord, Ohio, is an American company that designs and makes engine gaskets and sealing parts. It built its name on custom gaskets cut to the bore and thickness required, all made in the United States from American raw materials.

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 93 mm bore of the gaskets offered 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-AA360.

Important: the part numbers on this page suit only the EJ20 and EJ20E engines: check your vehicle's engine code before ordering.

Why switch to a reinforced gasket?

When the original gasket reaches its limit, the reinforced gasket holds on: under higher combustion pressure it keeps its shape and does not flatten.

When power rises, through a turbo, a supercharger or a higher compression ratio, the head gasket is the first part to fail in the top end. On a flat engine with two cylinder heads, a leak means removing the head concerned: a reinforced gasket spares you that job.