Reinforced head gasket Mazda 2.3 Turbo L3-VDT

The Mazda engines covered

The L3-VDT is a 2.3 litre turbocharged petrol engine. It powers the Mazda 3 (BK, BL) MPS, Mazda 6 (GG) and CX-7 models listed in the compatibility table below.

The original gasket carries part number L3K9-10-271B. Mazda publishes neither its bore, nor its thickness, nor its construction. The engine takes one cylinder head gasket, sized for the standard combustion pressure; when that pressure climbs, the clamping force eases, the head lifts slightly and coolant seeps into a cylinder.

Reinforced cylinder head gaskets

Sealing does not rest on the gasket alone but also on the fasteners that press the head onto the block. Beyond 100 N/mm², a composite gasket compresses for good; the 301 stainless steel of MLS gaskets takes 517 N/mm², 5 times more, and recovers its shape at every combustion. Also inspect the head bolts: replace any bolt that is stretched or damaged.

This page brings together 20 Cometic part numbers, from the American maker of competition gaskets, with an 89 mm bore for 19 of them and 88 mm for H2754SPD034S, in two constructions: MLS, multi-layer steel, with 18 C4481 part numbers from 0.69 to 3.56 mm in 89 mm and H2754SPD034S in 0.86 mm in 88 mm, and MLX, with a chamber stopper, with part number C4970-028 in 0.71 mm. The engine takes only one gasket: order a single part number.

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 20 part numbers on this page have an 89 mm bore, except H2754SPD034S at 88 mm, so only those of the same bore can be compared directly.

Preparation and fitting

Before reassembly, check the flatness of the head and block mating faces with a straightedge and have them resurfaced if needed. Cometic gaskets arrive already coated: do not apply any sealing paste. Remember to clean the gasket faces carefully before assembly.

Technical guide

The two constructions offered

Cometic MLS Several stainless steel sheets, stamped and riveted together. Each outer sheet carries active beads tracing the outline of every cylinder and fluid passage. A moderate clamping load is enough to seal, and the bore distorts very little. This versatile gasket suits anything from a tuned naturally aspirated engine to light boost. The C4481 part numbers on this page are offered in this construction.

Cometic MLX The same base as the MLS, with a folded centre sheet forming a stopper around each combustion chamber. The stopper concentrates the clamping force around the bore and limits how far the gasket is crushed. It is designed for boosted engines and high combustion pressures. Part number C4970-028 on this page is offered in this construction.

Choosing bore and thickness

Gasket bore. The Cometic MLS (C4481) and the Cometic MLX (C4970-028) are both offered here in 89 mm, and H2754SPD034S in 88 mm.

Thickness. No thickness is published for the original gasket L3K9-10-271B. A thicker gasket enlarges the combustion chamber and lowers the compression ratio; a thinner one reduces it and raises the ratio.

Before opting for a thickness below the original, measure with a dial gauge how far the pistons protrude above the block deck: it shows the clearance remaining between piston and head.

The brand

Cometic Gasket, Inc. is an American company founded in 1989 and based in Concord, Ohio, which designs and builds gaskets and sealing parts for engines. It earned its name with made-to-measure gaskets, cut to the bore and thickness required, all made in the United States from American materials. Its part numbers for this Mazda engine are offered here in 89 mm and 88 mm.

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 largest bore of these gaskets, 89 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: L3K9-10-271B.

Important: the part numbers on this page suit only the L3-VDT engine: check your Mazda's engine code before ordering.

Why switch to a reinforced gasket?

When the original gasket is no longer enough, the reinforced gasket replaces it: under higher combustion pressure it keeps its shape instead of collapsing. For the Mazda on this page, it is the answer as soon as the engine goes beyond its original output.

Whether you add a turbo, raise the compression ratio or rev higher with livelier cams, the cylinder head gasket becomes the weak link of a high-output engine. A reinforced gasket prevents the leak and the head removal that goes with it, far costlier than the gasket. On this turbocharged engine, the reinforced gasket is the first item to address once you go beyond the original output.