Reinforced cylinder head gasket Volvo 2.3 B23 B230 B234

The Volvo engines covered

The Volvo engines on this page, of 2.3 litres capacity, with 8 and 16 valves, carry the codes B23A, B23E, B23ET, B23F, B230A, B230E, B230ET, B230F, B230FB, B230FD, B230FK, B230FT, B230FT+, B230G, B230GT, B230K, B234F and B234G. They power the Volvo 240, 740, 760, 780, 940 and 960 in the table below, from 1978 to 1998. With a single cylinder head, the gasket is sold individually: one is needed per engine.

The original gasket carries the part numbers 1 378 646-2 and 3 514 521; the B230K takes the part numbers 1276191, 1276191-0 and 1332644. Volvo publishes neither its bore, nor its thickness, nor its construction. It is sized for standard combustion pressure: when that rises, the clamping load drops, the head lifts and coolant reaches a cylinder.

Reinforced cylinder head gaskets

Sealing does not depend on the gasket alone: it also rests on the fasteners that clamp the head to the block. A composite gasket is crushed for good beyond 100 N/mm², whereas the 301 stainless steel of the MLS withstands 517 N/mm², 5 times more, and regains its shape at every combustion. With the O-Ring, the stainless ring isolates the combustion chamber on its own, and the body of the gasket closes the water and oil circuits.

This page brings together the part numbers of two racing manufacturers, Athena and Cometic, in two constructions: the stainless-ring O-Ring from Athena, the multilayer MLS from Athena and from Cometic. Gasket bores run from 97 to 100 mm and thicknesses from 1.14 to 2 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

The volume of a gasket is the room it leaves free above each cylinder. It comes on top of the combustion chamber: the bigger it is, the lower the compression ratio falls. Only compare these volumes between gaskets of the same bore.

Preparation and fitting

Before fitting the gasket, check with a straightedge that the cylinder head and block are flat, and have them resurfaced if needed. There is no need to add sealant: Athena and Cometic supply their gaskets already coated.

Technical guide

The three constructions offered

	O-Ring / Cut Ring Athena A steel core lined with asbestos-free aramid fibre, around which a stainless compression ring is crimped at each cylinder. The ring shifts the clamping load onto a narrow band, right where the seal is decided, and a silicone bead keeps the water and oil passages safe. It is the construction that copes best with high combustion pressures, intended for the most heavily stressed engines.
	Athena MLS Two to five AISI 301 stainless steel sheets, laser-cut, embossed and riveted. One of them is folded around each cylinder to form a Gas Stopper that steers the clamping load toward the combustion chamber, while raised features close off the water and oil circuits. The outer faces receive a coating: one layer tolerates heat and makes up for small flaws in the block and head, a silicone layer prevents the gasket from bonding at removal. It is Athena's all-steel solution, from the tuned naturally aspirated engine to moderate boost.
	MLS Cometic A stack of stainless steel sheets, embossed and then riveted. Around each cylinder and each fluid passage, the outer sheets carry active beads that make the seal under a moderate clamping load, with limited bore distortion. It is the versatile construction, from the tuned naturally aspirated engine to light boost; here it comes in 100 mm, in 1.14 mm thickness.

Choosing bore and thickness

Gasket bore. The Athena O-Ring comes in 97.1 mm, the Athena MLS in 97 mm and the Cometic MLS in 100 mm.

Thickness. Volvo publishes no thickness for the 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 manufacturer does not publish the original thickness, use a dial gauge to measure how far the pistons stand proud of the block deck: this figure gives the clearance left between piston and cylinder head, particularly with the thinnest gasket.

The two brands

	Athena S.p.A. is an Italian company that designs gaskets and engine parts in Alonte, in the Veneto, where its main plant also stands. It has further sites in Spain, the United States, Brazil and India. Its multilayer gaskets are fitted as original equipment by car makers, and its whole racing range is designed and produced in Italy.
	Cometic Gasket, Inc. was founded in 1989 in Concord, Ohio. This American manufacturer makes gaskets and sealing solutions for engines. It specialises in the made-to-measure gasket, in the bore and thickness wanted, produced entirely 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 bore of the gaskets offered (97 to 100 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: 1 378 646-2, 3 514 521; 1276191, 1276191-0, 1332644 (B230K).

Important: the gaskets on this page are listed for the Volvo 240, 740, 760, 780, 940 and 960 in the table, from 1978 to 1998. For any other vehicle, note the engine code before ordering.

Why switch to a reinforced gasket?

When the original gasket runs out of capacity, the reinforced one carries on: under higher combustion pressure, it holds its shape and does not collapse.

When boost climbs or the compression ratio is raised, the head gasket is the first link to fail in the top end. A reinforced gasket rules out the leak, and with it the cylinder head removal, a job out of all proportion to the cost of the part.