Reinforced head gasket Ford Mondeo V S-MAX Galaxy Focus ST 2.0 EcoBoost

The Ford engines covered

The 2.0 litre petrol engines with four valves per cylinder R9CB, R9CD, R9CF, R9CH, R9CI, R9DA, R9DB, R9DC, R9DD, TNCA, TNCB, TNCC, TNCD, TNCF and T20HDTX power the Ford Mondeo V, S-MAX, Galaxy III, Focus III ST, Maverick, Edge and Explorer models and the Lincoln MKT in the table below.

The original gasket of these engines carries part number 5149932, except for the TNCC, for which Ford does not publish a part number. Ford 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 moves away from the block and coolant reaches a cylinder.

Reinforced cylinder head gaskets

Sealing does not depend on the gasket alone: the fasteners that pull the head down onto the block count just as much. With the O-Ring, the stainless steel wire seals the combustion chamber by itself and the gasket body closes the water and oil circuits; with the MLS, the 301 stainless steel sheets withstand 517 N/mm², 5 times the stress at which a composite gasket settles for good, and regain their shape with every combustion.

This page brings together two part numbers from Athena, an Italian maker of competition gaskets, in two constructions: the O-Ring, a steel sheet faced with aramid fibre and ringed with a stainless steel wire, with part number 330151R, and the MLS, a stack of stainless steel sheets, with part number 338483R. Both have an 89 mm bore, with thicknesses of 1 and 1.25 mm. As a rule, choose a gasket bore at least 0.5 mm larger than the cylinders. Each part number is sold individually, one gasket per engine.

Technical specifications

A gasket's volume is the space it leaves free above each piston. It adds to the combustion chamber and lowers the compression ratio; since both gaskets here share the same 89 mm bore, only the thickness changes this volume.

Preparation and fitting

Before assembly, check the flatness of the head and of the block with a straight edge, and have either one resurfaced if needed. Athena gaskets are delivered ready to fit: add no sealing paste.

Technical guide

The two constructions offered

Athena O-Ring A steel sheet coated with asbestos-free aramid fibre, each cylinder of which is ringed with a stainless steel compression ring. The ring concentrates the clamping load on a narrow band, where the seal is made, and a silicone bead protects the water and oil passages. It is the construction that holds the highest pressures in the range.

Athena MLS A stack of two to five AISI 301 stainless steel sheets, laser cut, stamped then riveted. A folded sheet surrounds each cylinder and forms a Gas Stopper, which steers the clamping load towards the combustion chamber, while raised beads isolate the water and oil circuits. The outer faces are coated: one layer takes the heat and fills small flaws of the block and head, a silicone layer stops the gasket from sticking at removal. It is Athena's all-steel solution, from the prepared naturally aspirated engine to moderate boost. Beyond that, the O-Ring remains the construction that withstands the highest pressures.

Choosing bore and thickness

Gasket bore. The Athena O-Ring (330151R) and the Athena MLS (338483R) both come in 89 mm.

Thickness. For the original gasket, Ford communicates no thickness. A thicker gasket enlarges the combustion chamber and lowers the compression ratio; a thinner one reduces it and raises the ratio.

As the manufacturer leaves the original thickness unstated, use a dial gauge to measure how far the pistons stand proud of the block's gasket face, especially if you aim for 1 mm: it determines the clearance left between piston and head.

The brand

Athena S.p.A. is an Italian company specialising in gaskets and engine parts, with its head office and main plant in Alonte, in the Veneto; it also has sites in Spain, the United States, Brazil and India. Car makers fit its multi-layer gaskets as original equipment, and the whole competition range is designed and built in Italy.

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 (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: 5149932.

Important: the part numbers on this page only apply to the R9CB, R9CD, R9CF, R9CH, R9CI, R9DA, R9DB, R9DC, R9DD, TNCA, TNCB, TNCC, TNCD, TNCF and T20HDTX engines: note your vehicle's engine code before ordering.

Why switch to a reinforced gasket?

When the original gasket reaches its limits, the reinforced gasket takes over: under higher combustion pressure it keeps its shape and does not flatten.

When a turbo engine gets more boost or a higher compression ratio, the head gasket becomes the first weak link of the top end. A reinforced gasket avoids the leak, and the head removal that comes after it, a job far more costly than the part itself.