Reinforced cylinder head gasket Opel 20E 20N 20S 24E

The Opel engines covered

The Opel petrol engines 20E, 20N and 20S, of 2.0 litres, and 24E, of 2.4 litres, are fitted to the Ascona B, Rekord D and E, Manta B and Kadett C models listed below.

For the 20E, 20N and 20S engines, the original gasket carries the part numbers 6 07 971, 90 323 445 and 90 349 947; no original part number is given for the 24E. Opel publishes neither the bore, nor the thickness, nor the construction of these gaskets. They are made for standard pressure: if it rises, clamping loosens, the cylinder head lifts and coolant reaches a cylinder.

Reinforced cylinder head gaskets

The head gasket does not seal on its own: the fasteners that clamp the head to the block matter as much as it does. Above 100 N/mm², a composite gasket settles for good; the 301 stainless steel of MLS gaskets withstands 517 N/mm², 5 times more, and recovers its shape at every combustion.

This page gathers the part numbers of Cometic, an American maker of competition gaskets, in a single construction: the multi-layer steel MLS. The gaskets come in bores of 96, 97.5, 98 and 99 mm and in thicknesses from 0.76 to 3.05 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 void it leaves above each cylinder. It adds to the combustion chamber and reduces the compression ratio, the more so as it is large. Compare these values only between gaskets of the same bore.

Preparation and fitting

Before fitting, check the flatness of the head and block faces with a straight edge, then have them machined if needed. Do not apply sealing paste: Cometic gaskets are delivered coated.

Technical guide

The construction offered

MLS Cometic Stainless steel layers, stamped and assembled with rivets. The outer layers carry active beads around each cylinder and each fluid passage. Moderate tightening is enough to seal and the bore barely distorts. This versatile construction suits everything from the prepared naturally aspirated engine to moderate boost.

Choosing bore and thickness

Gasket bore. The Cometic MLS is offered in 96 to 99 mm (C1793), depending on the part number.

Thickness. Opel publishes no thickness for the original gaskets of these engines. A thicker gasket enlarges the combustion chamber and lowers the compression ratio; a thinner one reduces it and raises the ratio.

If you are aiming for a thickness below the original, first measure with a dial gauge the height of the pistons above the block deck: it sets the clearance left between piston and head.

The brand

Cometic Gasket, Inc. is an American company founded in 1989 in Concord, Ohio, specialising in engine gaskets and sealing solutions. It is known for the made-to-measure gasket, cut to the bore and thickness requested. All of its production stays in the United States, with 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 original gaskets, which Opel does not publish 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: 6 07 971, 90 323 445 and 90 349 947.

Important: the part numbers on this page cover the Opel engines 20E, 20N, 20S and 24E: check your vehicle's engine code, then the bore, before ordering.

Why switch to a reinforced gasket?

When the original gasket reaches its limit, the reinforced gasket carries on: at higher combustion pressure it keeps its shape and does not crush.

With a turbo, a supercharger or a raised compression ratio, the head gasket bears the heaviest loads of the top end. A reinforced gasket avoids the leak and the head removal that follows, with the vehicle off the road and the labour to pay twice.