Reinforced head gasket Honda 2.2 F22A1 F22A4 F22A6

The Honda engines covered

The F22A1, F22A4 and F22A6 petrol engines, 2.2 litre units, power the Honda Accord IV and Prelude IV models listed in the compatibility table below.

The original gasket carries the part number 12251-PT0-004. Its bore is 85.9 mm; the manufacturer publishes neither its construction nor its thickness. It is calibrated for the original combustion pressure: when that rises, the clamping load eases, the cylinder head lifts slightly and coolant passes into a cylinder.

Reinforced cylinder head gaskets

Sealing does not depend on the head gasket alone: it also rests on the fasteners, which press the cylinder head against the block. A composite gasket is crushed for good beyond 100 N/mm² of allowable stress, whereas the 301 stainless steel of MLX/MLS gaskets takes 517 N/mm², 5 times more, and regains its shape at each combustion.

This page presents the part numbers of the American maker Cometic, a specialist in competition gaskets, in two constructions: the MLX with chamber stopper, with an 86 mm bore, and the MLS, with an 85 mm bore. The thickness is 1.14 mm in both cases. Each part number is sold individually: one gasket per engine.

Technical specifications

A gasket's volume is the free space it leaves above each cylinder. Added to the combustion chamber, it lowers the compression ratio, and all the more as it is large. As the two part numbers do not share the same bore, compare their volumes with care: only gaskets of the same bore can be compared directly.

Preparation and fitting

Before fitting, check with a straight edge that the head and block are flat, and have them resurfaced if needed. Cometic gaskets are supplied coated: they are fitted without sealing paste.

Technical guide

The two constructions offered

	Cometic MLS A stack of embossed stainless steel sheets riveted together. The outer sheets carry beads that surround each cylinder and each fluid passage. Moderate tightening is enough to seal and the bore distorts little. It is a versatile construction, from the tuned naturally aspirated engine to moderate forced induction.
	Cometic MLX A multilayer stainless steel gasket whose folded centre sheet forms a stopper around each chamber. This stopper concentrates the clamping pressure around the bore and limits how far the gasket is crushed. This construction is made for forced induction engines and high combustion pressures.

Choosing bore and thickness

Gasket bore. The Cometic MLX is available here in 86 mm (C14018) and the MLS in 85 mm (C14017).

Thickness. Honda publishes no thickness for the original gasket. 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 is unknown, use a dial gauge to measure how far the pistons protrude above the block deck, especially after resurfacing: this figure sets the clearance between piston and head.

The brand

Cometic Gasket, Inc. is an American company created in 1989 in Concord, Ohio, specialising in gaskets and sealing solutions for engines. It is renowned for gaskets made to measure, at the bore and thickness requested. All its production is American, from American 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 85.9 mm bore of the original gasket 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: 12251-PT0-004.

Important: the part numbers on this page suit only the F22A1, F22A4 and F22A6 engines: check your vehicle's engine code before ordering.

Why switch to a reinforced gasket?

When the original gasket reaches the end of its capacity, the reinforced gasket takes over: under higher combustion pressure, it keeps its shape instead of settling.

When power rises, whether through a turbo, a supercharger or a raised compression ratio, the head gasket is the first part of the top end to give way. Choosing a reinforced gasket means protecting the engine: it avoids the failure and the head removal that follows.