Reinforced cylinder head gasket Volvo B23 B230 2.3L

The Volvo engines covered

The Volvo petrol engines B23A, B23E, B23F, B230A, B230E, B230F, B230FT and B230K, of 2.3 litres, are fitted to the Volvo 240, 740, 760, 780, 940 and 960 models detailed below.

The original gasket of these engines carries the part number 1 378 646-2. Volvo publishes neither its bore, nor its thickness, nor its construction. It is rated for standard pressure: when that climbs, clamping weakens, the cylinder head lifts and coolant reaches a cylinder.

Reinforced cylinder head gaskets

The head gasket does not seal alone: the fasteners that clamp the head to the block contribute as much as it does. Beyond 100 N/mm², a composite gasket settles for good; the 301 stainless steel of MLS gaskets takes 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 exist in a 97 mm bore, with one part number in 98 mm, and in 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

The volume of a gasket is the empty space it leaves over each cylinder. That space joins the combustion chamber and lowers the compression ratio, all the more when it is large. Compare these figures only between gaskets of identical 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. Apply no sealing paste: Cometic gaskets are delivered coated.

Technical guide

The construction offered

MLS Cometic Stainless steel layers, stamped and then fixed by 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 runs from the prepared naturally aspirated engine to moderate boost.

Choosing bore and thickness

Gasket bore. Cometic MLS is offered in 97 mm (C4499) and, on one part number, in 98 mm (C14094).

Thickness. Volvo publishes no thickness for the original gasket 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 settle on a thickness below the original, first measure with a dial gauge the height of the pistons above the block deck: that figure determines the clearance left between piston and head.

The brand

Cometic Gasket, Inc. is an American company, born in 1989 in Concord, Ohio, that makes engine gaskets and sealing solutions. It made its name with the made-to-measure gasket, cut to the bore and thickness requested. All of its production remains 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 gasket, which Volvo 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: 1 378 646-2.

Important: the part numbers on this page match the Volvo B23 and B230 engines listed above: note your vehicle's engine code, then check the bore, before ordering.

Why switch to a reinforced gasket?

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

With a turbo, a supercharger or a raised compression ratio, the head sees heavier loads and the gasket becomes the most stressed part of the top end. A reinforced gasket rules out the gas or coolant leak and the head removal that follows, with the vehicle off the road.