Reinforced cylinder head gasket Porsche 911 Carrera S 997 M97.01

The Porsche engines covered

The M97.01 and M97.01S engines are the 3.8 litre flat-six of the Porsche 911 (997) Carrera S and Carrera 4S, in coupé, cabriolet and Targa form. Both are listed in the compatibility table below. Each bank of three cylinders has its own cylinder head and its own gasket, so the engine needs two.

The original gasket carries part number 997 104 201 03. Porsche publishes neither its bore, nor its thickness, nor its construction. Sized for standard combustion pressure, it reaches its limit as soon as it rises: clamping load drops, the head lifts and coolant finds its way into a cylinder.

Reinforced cylinder head gaskets

Sealing also depends on the fasteners that press the heads onto the crankcase. A composite gasket is crushed for good beyond 100 N/mm²; the 301 stainless steel of an MLX gasket withstands 517 N/mm², 5 times more, and regains its shape at every combustion. Replace any head bolt that is stretched or marked.

This page presents part numbers H2582SP4032S, C4926-032 and C4926-040 from Cometic, the American maker of racing gaskets, in a single construction: MLX. The bore is 102 mm for the C4926 part numbers and 102.5 mm for the H2582SP4032S; the thickness is 0.81 mm for the H2582SP4032S and the C4926-032, and 1.02 mm for the C4926-040. Each part number is sold individually: plan on two gaskets per engine.

Technical specifications

A gasket's volume is the free space it leaves above each cylinder. It adds to the combustion chamber and lowers the compression ratio: the thicker the gasket, the larger that volume. Here the bore is 102 mm for two part numbers and 102.5 mm for the H2582SP4032S; the thickness is 0.81 mm or 1.02 mm.

Preparation and fitting

Before refitting the cylinder heads, check the flatness of each head and of the crankcase with a straight edge, and have the faces ground if necessary. Cometic gaskets are supplied coated: do not add any gasket sealant.

Technical guide

The construction offered

Cometic MLX A stack of stamped, riveted stainless steel sheets whose centre sheet is folded to form a stopper around the combustion chamber, with a high-temperature coating. Clamping force rises at that point without any extra bore distortion. It is the strongest all-steel construction, suited to high combustion pressures, here in 102 mm and 102.5 mm.

Choosing bore and thickness

Gasket bore. The Cometic MLX come in 102 mm (C4926-032 and C4926-040) and in 102.5 mm (H2582SP4032S).

Thickness. No thickness is published for the original gasket 997 104 201 03. 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 stand above the block's gasket face, especially before choosing the 0.81 mm: this reading gives the clearance left between piston and head.

The brand

Cometic Gasket, Inc. is an American manufacturer founded in 1989 in Concord, Ohio, that designs engine gaskets and sealing solutions. It made its name with the made-to-order gasket, produced to the bore and thickness required and manufactured in the United States.

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 gasket, which Porsche has not published 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: 997 104 201 03.

Important: the part numbers on this page only suit the M97.01 and M97.01S engines of the 911 (997) Carrera S and Carrera 4S: check the engine code of your Porsche before ordering.

Why switch to a reinforced gasket?

When the standard gasket reaches its limits, the reinforced gasket takes over: under higher combustion pressure it keeps its thickness instead of being squashed.

When an engine is run at high revs, on track or in a serious build, combustion pressure and thermal expansion put the head gasket under more strain than any other part of the top end. A reinforced gasket stops the leak and with it the costly removal of both cylinder heads.