Reinforced cylinder head gasket Ford YVDA C23HD0D

The Ford engines covered

The Ford 2.3 EcoBoost, engine codes YVDA and C23HD0D, is a turbocharged inline-four petrol engine with direct injection, 16 valves and 2,261 cc. It powers the Focus RS (YVDA) and the Mustang (C23HD0D) listed in the table below. With a single cylinder head, the gasket is sold individually: one is needed per engine.

The original gasket carries part number 2172426. Ford 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 lifts and coolant reaches a cylinder.

Reinforced cylinder head gaskets

The gasket does not guarantee the seal on its own: it also depends on the fasteners that clamp the head onto the block. A composite gasket is permanently crushed above 100 N/mm², whereas the 301 stainless steel of the MLS and MLX withstands 517 N/mm², 5 times more, and recovers its shape at every combustion. With the O-Ring, the stainless ring alone isolates the combustion chamber, and the body of the gasket 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 MLX with a combustion stopper from Cometic. The gasket bores run from 89 to 90.1 mm and the thicknesses from 0.914 to 1.524 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, one gasket per engine.

Technical specifications

The volume of a gasket is the space it leaves free above each cylinder. It adds to the combustion chamber: the larger it is, the lower the compression ratio. Compare these volumes only between gaskets of the same bore.

Preparation and fitting

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

Technical guide

The three constructions offered

	O-Ring / Cut Ring Athena A steel core dressed with asbestos-free aramid fibre, around which a stainless compression ring is crimped at each cylinder. The ring concentrates the clamping pressure on a narrow band, exactly where the seal is made, and a silicone bead protects the water and oil passages. It is the construction that best withstands high combustion pressures, the one for the hardest-worked engines.
	Athena MLS Two to five AISI 301 stainless steel sheets, laser-cut, embossed and riveted. A folded sheet surrounds each cylinder and forms a Gas Stopper that directs the clamping load toward the combustion chamber, while raised beads seal off the water and oil passages. A coating covers the outer faces: one layer withstands heat and fills small imperfections in the block and cylinder head, a silicone layer stops the gasket from sticking at removal. It is Athena's all-steel solution, from the tuned naturally aspirated engine to moderate boost.
	MLX Cometic Embossed, riveted stainless steel sheets, including a folded centre sheet that forms a stopper around the combustion chamber, all under a high-temperature coating. The clamping load rises locally without distorting the bore any further. It is the toughest of the all-steel gaskets, for high boost pressures; here it comes in 89 mm, in four thicknesses.

Choosing bore and thickness

Gasket bore. The Athena O-Ring comes in 90 mm, the Athena MLS in 90.1 mm and the Cometic MLX in 89 mm.

Thickness. Ford does not publish any 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.

Since the manufacturer does not publish the original thickness, use a dial gauge to measure how far the pistons stand above the block deck: it sets the clearance left between piston and cylinder head, especially if you choose the thinnest gasket.

The two brands

	Athena S.p.A. designs gaskets and engine parts from its headquarters in Alonte, in the Veneto, where its main plant is also located. The company has other sites in Spain, the United States, Brazil and India. Its multilayer gaskets are fitted by car makers as original equipment, and its racing range is entirely designed and made in Italy.
	Cometic Gasket, Inc., founded in 1989 in Concord, Ohio, is an American maker of gaskets and sealing solutions for engines. Its speciality is the made-to-order gasket, in the bore and thickness requested, built 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 (89 to 90.1 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: 2172426.

Important: the Athena gaskets on this page are listed for the Focus RS (YVDA, from 2015 to 2018) and the Cometic MLX for the Focus RS (from 2016 to 2018) and the Mustang (C23HD0D, from 2020 to 2023). For any other vehicle, check the engine code before ordering.

Why switch to a reinforced gasket?

Where the original gasket reaches its limits, the reinforced one takes over: at higher combustion pressure, it keeps its shape instead of being crushed.

When the turbo pushes harder or the compression ratio goes up, the head gasket is the first part of the top end to give way. A reinforced gasket prevents the leak, and the cylinder head removal that follows, a job far more expensive than the part itself.