Reinforced head gasket Honda 2.2 F22B1 F22B4 F22B5 F22B8 and 2.3 F23A1

The Honda engines covered

The petrol engines F22B1, F22B4, F22B5 and F22B8 of 2.2 litres, together with the F23A1 of 2.3 litres, are sixteen-valve units that power the Honda Accord V and VI, Shuttle and Odyssey models in the compatibility table below. Each takes a single cylinder head gasket.

Two original gaskets are listed: 12251-P0A-004 for the F22B1, F22B4, F22B5 and F22B8 engines, and 12251-PAA-A01 for the F23A1. Honda publishes neither their bore, nor their thickness, nor their construction. 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 seal on its own: the fasteners that clamp the cylinder head onto the block provide the other half. A composite gasket settles for good beyond 100 N/mm² of stress, whereas the 301 stainless steel of MLS gaskets withstands 517 N/mm², 5 times more, and springs back with every combustion.

This page presents four Cometic part numbers, an American maker of competition gaskets, in a single construction: MLS. The bores run from 86 to 89 mm in 1 mm steps and the thickness is 0.69 mm. By convention, the gasket bore exceeds the cylinder bore by at least 0.5 mm, so you pick the bore according to whether the block is standard or rebored. Each part number is sold individually, one gasket per engine: order the one whose bore suits your block.

Technical specifications

Gasket volume is the space the gasket leaves free above each cylinder. That space is added to the combustion chamber and so pushes the compression ratio down; a comparison only makes sense between gaskets of the same bore.

Preparation and fitting

Before fitting the gasket, check with a straight edge that the cylinder head and block are flat, and have them resurfaced if necessary. Cometic supplies its gaskets already coated, so no sealing paste is needed.

Technical guide

The construction offered

Cometic MLS A stack of stamped stainless steel sheets, then riveted. The outer sheets show active beads around every cylinder and every fluid passage. Sealing is achieved with a moderate clamping load and little bore distortion. It is a versatile choice, from the prepared naturally aspirated engine to moderate forced induction.

Choosing bore and thickness

Gasket bore. The Cometic MLS gasket comes here in 86 mm (C4618-027), 87 mm (C4619-027), 88 mm (C4620-027) and 89 mm (C4621-027).

Thickness. Honda 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.

As Honda gives no original thickness, use a dial gauge to measure how far the pistons stand above the top of the block, particularly if the removed gasket is thinner than 0.69 mm: the reading gives the free clearance between piston and cylinder head.

The brand

Cometic Gasket, Inc. was founded in 1989 in Concord, Ohio. This American company makes gaskets and sealing parts for engines and has built its name on custom gaskets, made to the bore and thickness requested. All of its production is American, from raw materials sourced in the country.

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 maximum bore of 89 mm of the gaskets offered 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-P0A-004 and 12251-PAA-A01.

Important: the part numbers on this page only suit the engines F22B1, F22B4, F22B5, F22B8 and F23A1; the C4618 (86 mm) is reserved for the F22B engines, whereas the C4619, C4620 and C4621 also suit the F23A1: check your vehicle's engine code before ordering.

Why switch to a reinforced gasket?

When the original gasket reaches its limits, the reinforced gasket steps in: under higher combustion pressure it keeps its shape instead of being crushed.

When a turbo or supercharger is fitted, or the compression ratio is raised, the head gasket is the first link to give way in the top end. A reinforced gasket prevents the leak and, above all, the cylinder head removal that follows, which costs far more than the gasket itself.