Reinforced head gasket Opel 2.0 16V Turbo Z20LET Z20LEH X20XEV

The Opel engines covered

The Opel Z20LET is the 2.0-litre 16-valve DOHC turbocharged inline four-cylinder petrol engine of the Astra G, Zafira A and Speedster; the Z20LEH is its version in the Astra H and Zafira B, and the X20XEV the naturally aspirated version. This page covers these three engines with the Athena part numbers; the Cometic part numbers are listed for the Z20LET only.

The Z20LEH and X20XEV take other original gaskets: 93 185 757 or 56 07 891 on the Z20LEH, 90 509 849 or 93 188 114 among others on the X20XEV. On the Z20LET, the original gasket carries part number 93 180 271 or 56 07 867. It is a multi-layer steel (MLS) gasket with a 87.7 mm bore, whose thickness Opel 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 brings together the part numbers from two racing manufacturers, Athena and Cometic, in two constructions: Athena MLS with Gas Stopper and Cometic MLS multi-layer steel. Gasket bores run from 87.5 to 88.5 mm, covering the standard block as well as the rebored block, and thicknesses from 1.00 to 2.34 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: 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. None of these gaskets requires sealant: Athena and Cometic both supply them already coated.

Technical guide

The two constructions offered

Athena MLS Two to five layers of AISI 301 stainless steel, laser cut, stamped and riveted. Around each cylinder, a layer folded over on itself, the Gas Stopper, concentrates the clamping load on the combustion chamber, while beads seal the water and oil passages. The outer layers receive a two-coat finish: the first withstands high temperatures and fills small irregularities on the block and cylinder head, the second, silicone based, keeps the gasket from sticking on disassembly. This is Athena's all-steel choice, from a prepared naturally aspirated engine to moderate forced induction.

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 Athena MLS comes in 87.5, 88 and 88.5 mm, the Cometic MLS in 88 mm.

Thickness. Opel 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 two brands

	Athena S.p.A. is an Italian manufacturer of engine gaskets and components, with its head office and main plant in Alonte, in the Veneto region. The group also produces in Spain, the United States, Brazil and India. Its multi-layer gaskets are fitted as original equipment by car manufacturers, and its racing range is designed and made entirely in Italy.
	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 87.7 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: 93 180 271, 56 07 867 (Z20LET) ; 93 185 757, 56 07 891 (Z20LEH) ; 90 509 849, 93 188 114 (X20XEV).

Important: the C20XE and C20LET of the previous generation, as well as the later 2.0-litre Ecotec turbo engines (A20NFT, A20NHT), 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.