Reinforced cylinder head gasket Ford 2.3 OHC

The Ford engines covered

The Ford 2.3-litre OHC petrol engine powers in particular the Pinto, Mustang II, Mustang, Fairmont, Granada, LTD, Thunderbird, Courier, Ranger and Aerostar in the compatibility table below, whose applications are those published by Cometic.

Two original gaskets are listed: D42E-6051-AC for the 92Y, 99BT, A140, LL23 and R23 engines, and 3593361 for the L99A. Ford publishes neither the bore, nor the thickness, nor the construction of these gaskets. They are calculated for the standard combustion pressure: when it rises, the clamping load fades, the cylinder head lifts off the block and coolant finds its way into a cylinder.

Reinforced cylinder head gaskets

The gasket does not make the seal on its own: it also depends on the fasteners that clamp the head against the block. A composite gasket crushes for good beyond 100 N/mm² of admissible stress, whereas the 301 stainless steel of MLS gaskets withstands 517 N/mm², 5 times more, and recovers its shape at every combustion. The O-Ring divides the roles differently: its stainless ring alone seals combustion, the body handles the water and oil circuits, and nothing needs machining in the block.

This page brings together the part numbers from two racing manufacturers, Athena and Cometic, in two constructions: O-Ring with a stainless ring for Athena and MLS multi-layer steel for Cometic. Gasket bores run from 97.3 to 100.1 mm and thicknesses from 0.69 to 3.05 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: the empty space remaining above each cylinder across the thickness of the gasket. It adds to the combustion chamber, so the larger it is, the lower the compression ratio. Compare these figures only between gaskets of the same bore.

Preparation and fitting

Before installing the gasket, lay a straightedge across the head and the block to check flatness, then have the face that needs it machined flat. These gaskets go on without sealant: both Athena and Cometic deliver them already coated.

Technical guide

The two constructions offered

Athena O-Ring / Cut Ring A steel plate covered with asbestos-free aramid fibre, with a stainless steel compression ring around each cylinder. The ring carries the clamping load onto a small diameter, exactly where the seal is made, while a silicone bead protects the water and oil passages. No other construction withstands such high pressures, and this is the only one suited to a head already fitted with a compression wire.

Cometic MLS Several stainless steel sheets, embossed, stacked and then riveted. The outer sheets show active beads around each cylinder and each fluid passage. Moderate clamping is enough to seal, and the bore distorts little. A versatile gasket, suited from the tuned naturally aspirated engine to moderate forced induction.

Choosing bore and thickness

Gasket bore. The Athena O-Ring comes in 99.6 mm (330132R), the Cometic MLS in 97.3 mm (C5369-040, C5369-051, C5369-060, C5369-066, C5369-075, C5369-080, C5369-120) and in 100.1 mm (C5709-027, C5709-040, C5709-051, C5709-060, C5709-080, C5709-120).

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

With no published original thickness, use a dial gauge to measure how far the pistons stand proud of the block deck, particularly if you choose 0.69 mm: it shows the clearance left between piston and head.

The two brands

	Athena S.p.A. is an Italian maker of gaskets and engine components, headquartered with its main plant in Alonte, in the Veneto region. It also produces in Spain, the United States, Brazil and India. Its multi-layer gaskets are fitted as original equipment by car makers, and its entire racing range is designed and built in Italy.
	Cometic Gasket, Inc. was founded in 1989 in Concord, Ohio. This American maker of engine gaskets and sealing solutions owes its reputation to the made-to-measure gasket, cut to the bore and thickness required, and to production carried out entirely in the United States with local raw 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, 97.3, 99.6 and 100.1 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: D42E-6051-AC and 3593361.

Important: the part numbers on this page fit only the Ford 2.3-litre OHC engine of the applications in the compatibility table: check the bore of your engine before ordering, as the gaskets come in two bore families.

Why switch to a reinforced gasket?

Once the original gasket reaches its limits, the reinforced gasket steps in: under a higher combustion pressure it does not crush and keeps its geometry.

Turbo, supercharger or a raised compression ratio on the Ford 2.3-litre OHC engine: the head gasket is the first weak link of the top end. A reinforced gasket avoids the leak and the head removal that follows, a job far dearer than the part.