Reinforced cylinder head gasket Mitsubishi 4G63 4G63-T G4CP-D Eagle Talon Hyundai Sonata

The Mitsubishi engines covered

The 2.0-litre G4CP-D, 4G63 and 4G63-T engines power the Hyundai, Eagle, Proton, Dodge, Soueast, JMC and other vehicles in the compatibility table below; the 4G63-T is the turbocharged version. The head gasket is sold individually, one per engine.

For the G4CP-D, the original gasket carries part number MD-113173; the manufacturer publishes neither its bore, its thickness nor its construction. For the 4G63 and the 4G63-T, no original part number is confirmed. A standard gasket is sized for standard combustion pressure: when it rises, the clamping load fades, the head lifts and coolant passes into a cylinder.

Reinforced cylinder head gaskets

Sealing does not depend on the gasket alone: the fasteners that clamp the head onto the block contribute just as much. A composite gasket settles permanently beyond 100 N/mm² of admissible stress, whereas the 301 stainless steel of MLS gaskets withstands 517 N/mm², 5 times more, and regains its shape on every combustion. With the O-Ring, the stainless ring seals the combustion chamber on its own and the gasket body closes water and oil.

This page brings together 20 part numbers from two racing makers, Athena and Cometic, in four constructions: the stainless-ring O-Ring and the multilayer MLS from Athena, the multilayer MLS and the copper from Cometic. Bores run from 85.3 to 88.3 mm and thicknesses from 0.95 to 1.60 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 void it leaves above each piston. That void adds to the combustion chamber and lowers the compression ratio; only gaskets of the same bore should be compared.

Preparation and fitting

Before fitting, check the flatness of the head and the block with a straightedge, and have the warped part resurfaced. Add no sealing paste: Athena and Cometic supply their gaskets already coated.

Technical guide

The four constructions offered

	Cometic Copper A sheet of oxygen-free copper, grade C110 (99.9% copper). The metal resists corrosion, deforms without cracking, carries heat away well and stays ductile at high temperature. Cometic checks the flatness of every piece and advises fitting it with a crimped sealing ring for the best result.
	Cometic MLS A stack of embossed, riveted stainless steel sheets. The outer sheets carry active beads around each cylinder and each fluid passage. A moderate clamping load is enough to seal, with little bore distortion: it is the versatile gasket, from the built naturally aspirated engine to moderate boost.
	Athena MLS Two to five layers of AISI 301 stainless steel, laser-cut, embossed and then riveted. Around each cylinder, a sheet folded back on itself, the Gas Stopper, brings the clamping force back toward the combustion chamber, while beads isolate water and oil. The outer faces are coated: a first layer withstands heat and fills small flaws in the block and head, a second, silicone layer stops the gasket sticking at removal. It is Athena's all-steel solution, from the built naturally aspirated engine to moderate boost. The beads work like springs: they regain their shape on every heat and cool cycle, which keeps the sealing pressure up across the whole rev range.
	Athena O-Ring / Cut Ring A steel body loaded with asbestos-free aramid, with a stainless ring crimped around each cylinder. The ring concentrates the clamping force on a narrow band, exactly where sealing is decided, while a silicone bead closes the water and oil passages. It is the construction that best withstands high combustion pressure, and it fits without machining the head or the block, even on a heavily tuned engine.

Choosing bore and thickness

Gasket bore. The Athena O-Ring comes in 86.3 mm (330038R), 86.6 mm (330058R) and 87.5 mm (330042R); the Athena MLS in 85.3, 86.3, 87.5 and 88.3 mm; the Cometic MLS in 87 mm (H1528SP6060S) and 88 mm (H1538SP1045S); the Cometic copper in 85.5 mm (H1536SP2063C), in that bore only.

Thickness. The manufacturer gives no thickness for its 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, read with a dial gauge how far the pistons stand above the block's gasket face: it sets the clearance left between piston and head, above all with the thinnest gaskets.

The two brands

	Athena S.p.A. is an Italian company making engine gaskets and parts, with its head office and main plant in Alonte, in the Veneto; it has other sites in Spain, the United States, Brazil and India. Vehicle makers fit its multilayer gaskets as original equipment, and its racing range is designed and built in Italy.
	Cometic Gasket, Inc. is an American maker of engine gaskets and sealing solutions, based in Concord, Ohio, since 1989. It is known for the gasket made on request, to the bore and thickness wanted, built entirely 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 bore of the gaskets offered (85.3 to 88.3 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: MD-113173 for the G4CP-D.

Important: these gaskets are listed for the G4CP-D, 4G63 and 4G63-T engines in the table below: read your vehicle's engine code before ordering, then choose the bore and thickness you need.

Why switch to a reinforced gasket?

When the standard gasket reaches its limit, the reinforced gasket keeps its shape under higher combustion pressure instead of crushing.

An engine that is built, boosted harder or compressed more loads the head gasket first. A reinforced gasket prevents the leak and, above all, a second head removal, a job far more expensive than the part. Reinforcing the gasket is therefore a safety measure rather than a comfort, because it protects the engine and the work already done on it.