Reinforced head gasket Subaru Impreza Legacy Forester 2.0 SOHC EJ20 EJ201 EJ20E

The Subaru engines covered

The Subaru EJ20 is the 2.0-litre boxer four-cylinder petrol engine of the Impreza, Legacy and Forester. This page covers its 16-valve SOHC versions EJ20E and EJ201, for which Cometic lists its C4360 gaskets.

On the EJ20E and EJ201, the original gasket carries part number 11044-AA360 or 11044-AA364. It is a multi-layer steel (MLS) gasket with a 93 mm bore, whose thickness Subaru does not publish. It is sized for standard combustion pressure: when that pressure rises, clamping load drops, the cylinder head lifts, and coolant passes into a cylinder.

Reinforced cylinder head gaskets

A cylinder head gasket does not create the seal on its own: it holds because the fasteners clamp the head against the block. A composite gasket is crushed for good beyond 100 N/mm² of admissible stress, whereas the 301 stainless steel of the MLS gaskets withstands 517 N/mm², 5 times more, and springs back at every combustion.

This page offers the part numbers from Cometic, a racing manufacturer, in MLS multi-layer steel construction. Gasket bores run from 103 to 103 mm, covering the standard block as well as the rebored block, and thicknesses from 0.69 to 3.56 mm, enough to adjust the compression ratio without touching the pistons or the cylinder head. As a rule, the gasket bore chosen is at least 0.5 mm larger than the actual cylinder bore. Each part number is sold individually: a boxer engine needs two gaskets, one per cylinder head.

Technical specifications

Gasket volume: the space the gasket leaves above each cylinder. It enlarges the combustion chamber, and the larger it is, the lower the compression ratio. Values compare with one another at identical gasket bore.

Preparation and fitting

Before fitting, check the flatness of the cylinder head and of the block with a straight edge and have them skimmed if necessary. These gaskets require no sealant: Cometic supplies them already coated.

Technical guide

The construction offered

Cometic MLS Several stamped and riveted stainless steel layers. The outer layers carry active beads around each cylinder and each fluid passage. Sealing is achieved with a moderate clamping load and limited bore distortion. This is the versatile choice, from a prepared naturally aspirated engine to light forced induction.

Choosing bore and thickness

Gasket bore. The Cometic MLS comes in 103 mm.

Thickness. Subaru does not publish the thickness of the original gasket. A thicker gasket enlarges the combustion chamber and lowers the compression ratio; a thinner one reduces it and raises the ratio.

With a thickness finer than that of the removed gasket, measure piston protrusion above the block with a dial gauge: it is what determines the remaining clearance between piston and cylinder head.

The brand

Cometic Gasket, Inc. is an American manufacturer of engine gaskets and sealing solutions, founded in 1989 and based in Concord, Ohio. Its speciality is the made-to-order gasket, in the bore and thickness required. All its products are made in the United States, from American 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 original gasket 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, 11044-AA364.

Important: the naturally aspirated (EJ204) and turbocharged (EJ205, EJ207) DOHC EJ20 take other cylinder head gaskets: they are not covered by this page.

Why switch to a reinforced gasket?

A reinforced gasket holds where the standard one reaches its limit: at higher combustion pressure it keeps its shape instead of being crushed.

As soon as power goes up, turbo, supercharger or raised compression ratio, the head gasket becomes the weak link of the top end. Switching to a reinforced gasket is then not a comfort but a safeguard: it is what prevents the failure and the head removal that comes with it.