Reinforced head gasket BMW M3 E30 2.0 2.3 16V S14B20 S14B23

The BMW engines covered

The BMW S14 is the 16-valve DOHC inline four-cylinder petrol engine of the M3 (E30); its 2.0-litre S14B20 version also powers the 320is. This page covers the S14B20 and S14B23: these engines take the same reinforced cylinder head gaskets.

The original gasket carries part number 11 12 1 316 714. BMW publishes neither its construction nor its thickness; its bore is 94 mm. 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 Cut Ring with stainless rings and Cometic MLS multi-layer steel. Gasket bores run from 90 to 96.5 mm, covering the standard block as well as the rebored block, and thicknesses from 0.69 to 3.56 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 Cut Ring A gasket in reinforced, asbestos-free MO115 material (steel core, aramid fibres, NBR binder), supplied with separate AISI 304 stainless steel rings around each cylinder. Athena also intends it for turbocharged or nitrous engines above 2 bar, with no machining of the cylinder head or block. A silicone bead reinforces the sealing of the water and oil passages. On fitting, the ring embossments face the cylinder head. Athena rates the MO115 material at 100 N/mm² at most: the stainless rings are what hold combustion.

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 Cut Ring comes in 95 mm, the Cometic MLS in 90, 93.4, 94.5, 95, 95.5, 96 and 96.5 mm.

Thickness. BMW 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 94 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: 11 12 1 316 714.

Important: the S14B25 takes another original gasket (11 12 1 316 907), and the S38 six-cylinder engines take other gaskets again: 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.