Reinforced cylinder head gasket Mitsubishi Lancer Evolution X 4B11T

The Mitsubishi engines covered

The turbocharged 2.0-litre 4B11T petrol engine powers the Mitsubishi Lancer Evolution X, including the FQ-330, FQ-360, FQ-400 and FQ-440 versions, as well as the Lancer and Lancer Sportback Ralliart, from 2007 to 2016, as shown in the table below.

The original gasket carries part number 1005B450. Mitsubishi publishes neither its bore, nor its thickness, nor its construction. It is sized for standard combustion pressure: when that rises, the clamping load drops, the head moves away from the block and coolant reaches a cylinder.

Reinforced cylinder head gaskets

The gasket alone does not provide the seal: the bolts that clamp the head onto the block count just as much. A composite gasket sets permanently above 100 N/mm², whereas the 301 stainless steel of MLS and MLX gaskets withstands 517 N/mm², 5 times more, and recovers its shape at every combustion. With the O-Ring, the stainless ring isolates the combustion chamber by itself while the gasket body closes the water and oil circuits.

This page brings together the part numbers of two racing manufacturers, Athena and Cometic, in three constructions: the stainless-ring O-Ring and the multilayer MLS from Athena, the chamber-stop MLX from Cometic. Gasket bores run from 87.5 to 90 mm and thicknesses from 1.0 to 1.2 mm, enough to tune the compression ratio without touching the pistons or the 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, one gasket per engine.

Technical specifications

A gasket's volume is the free space it leaves above each cylinder. That space adds to the combustion chamber: the bigger it is, the lower the compression ratio falls. Only compare these volumes between gaskets of the same bore.

Preparation and fitting

Before fitting, check the flatness of the head and the block with a straightedge, and have whichever needs it resurfaced. No sealant is needed: Athena and Cometic supply their gaskets already coated.

Technical guide

The three constructions offered

	O-Ring / Cut Ring Athena A steel core sheathed in asbestos-free aramid fibre, with a crimped stainless compression ring around each cylinder. The ring focuses the clamping load on a narrow strip, where the seal is actually made, while a silicone bead shuts off the water and oil passages. It is the construction that holds high combustion pressures best, the one chosen for the hardest-working engines.
	MLS Athena Two to five sheets of AISI 301 stainless steel, laser cut, embossed and riveted. A folded sheet surrounds each cylinder and forms a Gas Stopper that steers the clamping load towards the combustion chamber, while ridges isolate the water and oil circuits. A coating covers the outer faces: one layer resists heat and fills small flaws in the block and head, a silicone layer stops the gasket sticking at removal. It is Athena's all-steel solution, from the tuned naturally aspirated engine to moderate boost. Its thin layers let the gasket follow the small movements of the head under load and keep an even clamping pressure along the whole sealing line, cylinder after cylinder.
	MLX Cometic Embossed, riveted stainless steel sheets, including a folded centre sheet that forms a stopper around the combustion chamber, under a high-temperature coating. The clamping load rises at that point without deforming the bore any further. It is the strongest all-steel gasket, designed for high boost; it is offered here in 88 and 90 mm, in a single thickness.

Choosing bore and thickness

Gasket bore. The Athena O-Ring comes in 89 mm, the Athena MLS in 87.5 mm and the Cometic MLX in 88 mm and 90 mm.

Thickness. Mitsubishi communicates no thickness for the original gasket. 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, measure with a dial gauge how far the pistons protrude above the deck of the block: it fixes the clearance between piston and head, above all with the thinnest gasket.

The two brands

	Athena S.p.A. is an Italian manufacturer of gaskets and engine parts. Its head office and main factory are in Alonte, in the Veneto, and it runs further sites in Spain, the United States, Brazil and India. Its multilayer gaskets are used as original equipment on vehicles, and its whole competition range is designed and produced in Italy.
	Cometic Gasket, Inc. is an American company, founded in 1989 in Concord, Ohio, that makes gaskets and sealing solutions for engines. Its know-how is the made-to-measure gasket, in the bore and thickness requested, produced entirely 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 bore of the gaskets offered (87.5 to 90 mm) 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: 1005B450.

Important: the gaskets on this page are listed for the 2.0-litre turbo Mitsubishi 4B11T engine in the table (2007 to 2016). For any other vehicle, note the engine code before ordering.

Why switch to a reinforced gasket?

When the original gasket reaches the end of its capacity, the reinforced gasket replaces it: under higher combustion pressure it holds its shape instead of flattening.

Fitting a turbo or a supercharger, or raising the compression ratio, is enough to make the head gasket the weak point of the top end. A reinforced gasket avoids the leak and the head removal that follows, a job costing far more than the part.