Reinforced cylinder head gasket Ford C23HDEX and Mazda LF-VE, L3-VE, L5-VE

The Ford and Mazda engines covered

The Ford C23HDEX 2.3-litre petrol engine and the Mazda LF-VE 2.0-litre, L3-VE 2.3-litre and L5-VE 2.5-litre petrol engines power the Ford Focus I and Fusion as well as the Mazda 3, 5, 6, CX-7, MX-5, MPV III, Tribute and Biante listed below.

The original gasket of these engines carries the part numbers L3G2-10-271A and L309-10-271 (C23HDEX, LF-VE), 1 124 372 (L3-VE) and L501-10-271 (L5-VE). Ford and Mazda publish neither the bore, nor the construction, nor the thickness of these gaskets. The series fitting is calculated for the factory combustion pressure: once it rises, the clamping load weakens, the cylinder head lifts and coolant enters a cylinder.

Reinforced cylinder head gaskets

The head gasket does not seal alone: the fasteners that press the head onto the block play just as large a part. Above 100 N/mm², a composite gasket compresses without recovery; the 301 stainless steel of MLS gaskets withstands up to 517 N/mm², 5 times more, and springs back on every combustion.

This page brings together the part numbers of Cometic, an American maker of racing gaskets, for one construction only: the multi-layer steel MLS. Every gasket has a 90 mm bore 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 means the clearance the gasket creates above each cylinder. That space is added to the combustion chamber volume and lowers the compression ratio, and the larger it is, the greater the drop. Set these values against each other only for gaskets of the same bore.

Preparation and fitting

Before assembly, check with a straight edge that the head and block faces are flat, and have them resurfaced if necessary. Do not apply sealing paste: Cometic gaskets are supplied already coated.

Technical guide

The construction offered

MLS Cometic Stainless steel sheets stamped and then riveted together. The outer sheets carry active beads around every cylinder and every fluid passage. A moderate tightening torque is enough to seal, and the bore distorts very little. This versatile solution runs from the prepared naturally aspirated engine to moderate boost.

Choosing bore and thickness

Gasket bore. The Cometic MLS exists in 90 mm (C5906), and only in that bore.

Thickness. Ford and Mazda do not state 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.

If you choose a thickness smaller than the original, use a dial gauge to measure how far the pistons stand proud of the block deck: it gives the clearance left between piston and head.

The brand

Cometic Gasket, Inc. is an American maker of engine gaskets and sealing solutions, founded in 1989 in Concord, Ohio. Its speciality is the made-to-measure gasket, cut to the bore and thickness requested. All of its production stays in the United States, using 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 the manufacturers do not state 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: L3G2-10-271A, L309-10-271, 1 124 372 and L501-10-271.

Important: the part numbers on this page fit only the C23HDEX, LF-VE, L3-VE and L5-VE engines: check your vehicle's engine code before placing an order.

Why switch to a reinforced gasket?

When the original gasket reaches the end of its life, the reinforced gasket takes over: under a higher combustion pressure it keeps its shape and does not crush.

Turbo, supercharger or a raised compression ratio: the head gasket takes the load first, it is the most stressed part of the top end. A reinforced gasket prevents the leak and the head removal that follows, with the car off the road.