Reinforced head gasket Hyundai Genesis Coupé 2.0 G4KF

The Hyundai and Kia engines covered

The G4KF petrol engine, a 2.0 litre turbo four-cylinder from the Theta II family, powers the Hyundai Genesis Coupé models in the compatibility table below.

This original gasket carries the part number 22311-2C000. Its bore is 88 mm; Hyundai publishes neither its construction nor its thickness. It is designed for standard combustion pressure: when that pressure rises, the clamping force drops, the cylinder head lifts slightly and coolant enters a cylinder.

Reinforced cylinder head gaskets

The head gasket does not create the seal on its own: the seal is held by the fasteners, which press the cylinder head against the block. A composite gasket is crushed for good beyond 100 N/mm² of allowable stress, whereas the 301 stainless steel of MLX gaskets withstands 517 N/mm², 5 times more, and recovers its shape at each combustion.

This page offers the part numbers from Cometic, the American maker of competition gaskets, in a single construction: the MLX with a combustion chamber stopper. The gasket bore, 88 mm, is the same as the original gasket, and two thicknesses are offered, 0.81 mm and 1.12 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

Gasket volume is the space it leaves above each cylinder. It is added to the combustion chamber and lowers the compression ratio, the more so as it grows. The values only make sense between gaskets of the same bore.

Preparation and fitting

Before fitting, check the flatness of the cylinder head and block with a straight edge, and have them resurfaced if needed. These gaskets are fitted without sealant, as Cometic supplies them already coated.

Technical guide

The construction offered

Cometic MLX A multi-layer stainless steel gasket whose folded centre layer forms a stopper around the combustion chamber, with a high-temperature coating. Clamping rises locally without adding to bore distortion. It is the most resistant of the all-steel gaskets, to be kept for severe boost; it is offered here in 88 mm only.

Choosing bore and thickness

Gasket bore. The Cometic MLX is only offered here in 88 mm (C4953).

Thickness. Hyundai does not disclose 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.

As the original thickness is not published, use a dial gauge to measure how far the pistons protrude above the block, especially with the thinner of the two thicknesses: that figure gives the clearance that remains between piston and cylinder head.

The brand

Founded in 1989 in Concord, Ohio, Cometic Gasket, Inc. designs gaskets and sealing solutions for engines. Its reputation comes from the gasket made to order, at the bore and thickness wanted. All its manufacturing stays in the United States, with 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 88 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: 22311-2C000.

Important: the part numbers on this page only apply to the G4KF engine: check your vehicle's engine code before placing an order.

Why switch to a reinforced gasket?

The reinforced gasket takes over where the original gasket reaches the end of its capacity: under higher combustion pressure, it keeps its shape instead of sagging.

With a turbo, a supercharger or a raised compression ratio, the head gasket is the first part to give way in the top end. A reinforced gasket is then a matter of safety as much as comfort: it spares you the failure and the cylinder head removal that goes with it.