Reinforced head gasket Ford 2.3 R23 and L99A

The Ford engines covered

The 2.3 litre Ford petrol engines R23 and L99A are fitted to the Ranger and Tempo models listed below.

These engines receive two original gaskets: part number D42E-6051-AC (R23), whose bore is not given, and part number 3593361 (L99A), with a 99.5 mm bore. Ford publishes neither their construction nor their thickness. They are designed for standard combustion pressure: when that pressure rises, the clamping load weakens, the cylinder head lifts and coolant seeps into a cylinder.

Reinforced cylinder head gaskets

A gasket alone does not guarantee a seal: the fasteners, which clamp the cylinder head to the block, play an equal part. A composite gasket withstands no more than 100 N/mm² before it is crushed for good, whereas the 301 stainless steel of MLS gaskets resists 517 N/mm², 5 times more, and regains its shape on every combustion.

This page presents the part number from Athena, an Italian maker of racing gaskets, for a single construction: the multi-layer steel MLS. The gasket has a 97.3 mm bore, against 99.5 mm for the original gasket 3593361, and a thickness of 1.00 mm. 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

A gasket's volume is that of the free space it creates above each cylinder. This volume adds to the combustion chamber: the larger it is, the lower the compression ratio. The figure is only compared between gaskets of the same bore.

Preparation and fitting

Run a straight edge over the cylinder head and the block before assembly to check they are flat, and have them machined if needed. The gasket arrives already coated by Athena: apply no sealing paste.

Technical guide

The construction offered

Athena MLS A pile of two to five layers of AISI 301 stainless steel, laser cut, stamped and then riveted. A folded layer surrounds each cylinder, forming a Gas Stopper that transfers the clamping force to the combustion chamber; beads isolate the water and oil circuits. Both outer faces carry two coating layers each: one withstands high temperatures and compensates for small flaws in the block and cylinder head, the other, in silicone, stops the gasket from sticking on removal. Athena makes it its all-steel solution, from a prepared naturally aspirated engine to moderate forced induction.

Choosing bore and thickness

Gasket bore. The Athena MLS is offered in 97.3 mm (338301R), in that bore only.

Thickness. Ford does not disclose the thickness of the original gaskets. A thicker gasket enlarges the combustion chamber and lowers the compression ratio; a thinner one reduces it and raises the ratio.

As the original thickness remains unknown, measure with a dial gauge by how much the pistons rise above the block, especially if the removed gasket exceeds 1.00 mm: this value determines the clearance available between piston and head.

The brand

Athena S.p.A. is an Italian maker of gaskets and engine components; its head office and main plant are in Alonte, in the Veneto. The group 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 born in Italy, from design to manufacture.

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 99.5 mm bore of the original gasket 3593361 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 number on this page fits only the engines R23 and L99A: check your vehicle's engine code before placing an order.

Why switch to a reinforced gasket?

When the standard gasket reaches the end of its capacity, the reinforced gasket takes over: under increased combustion pressure it keeps its thickness and shape.

Adding a turbo or a supercharger, or raising the compression ratio, exposes the head gasket above all, the most heavily loaded link of the top end. A reinforced gasket helps avoid the leak and the resulting removal of the cylinder head.