Reinforced head gasket Honda 2.0 K20C1 K20C4

The Honda engines covered

The K20C1 and K20C4 are 2.0 litre petrol engines with sixteen valves; the K20C1 is the turbocharged version. They power the Honda Civic IX Type R (FK2), Civic X Type R (FK8) and Accord X models in the compatibility table below, and each takes a single cylinder head gasket.

The original gasket carries part number 12251-RPY-G02. Honda does not publish its bore, thickness or construction. It is sized for standard combustion pressure; when it rises, the clamping load relaxes, the cylinder head lifts slightly and coolant finds its way into a cylinder.

Reinforced cylinder head gaskets

The gasket is only half of the seal: the other half comes from the fasteners that clamp the head to the block. A composite gasket settles for good beyond 100 N/mm², whereas the 301 stainless steel of MLS gaskets withstands up to 517 N/mm², 5 times more, and recovers its shape with every combustion.

This page brings together four part numbers from two competition makers, Athena (Italy) and Cometic (United States), all in multi-layer steel MLS construction. Cometic offers three: 0.71 mm and 1.07 mm for an 87 mm bore, and 0.71 mm for an 88 mm bore; Athena offers 1.0 mm for an 86.75 mm bore. The engine takes only one gasket: order a single part number, according to the bore and thickness you want.

Technical specifications

Gasket volume is the free space the gasket leaves above each piston. It comes on top of the combustion chamber and lowers the compression ratio; compare only gaskets with the same bore, since the part numbers on this page do not all share one.

Preparation and fitting

Before assembly, check the flatness of the head and block with a straight edge, and have them resurfaced if needed. Athena and Cometic gaskets are supplied coated: there is no need to add sealing paste.

Technical guide

The two constructions offered

Athena MLS Athena MLS Between two and five AISI 301 stainless steel sheets, laser cut, stamped and riveted. A folded sheet rings each cylinder: this Gas Stopper sends the clamping load back toward the combustion chamber, while beads close off the water and oil circuits. Each outer face receives a coating: one layer withstands high temperatures and fills small flaws in the block and head, a silicone layer keeps the gasket from sticking at removal. It is Athena's all-steel formula, suited from the prepared naturally aspirated engine to moderate forced induction.

Cometic MLS Stainless steel sheets, stamped and joined by rivets. The surface sheets carry beads that ring each cylinder and each coolant or oil channel. Sealing comes from moderate tightening, and the bore keeps its shape. This construction suits the prepared naturally aspirated engine as well as moderate forced induction.

Choosing bore and thickness

Gasket bore. The Cometic MLS is available here in 87 mm (C14014-028 and C14014-042) and 88 mm (C14021-028), and the Athena MLS in 86.75 mm (338500FR).

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

Since Honda does not state the original thickness, use a dial gauge to measure how far the pistons stand above the block face, particularly if you choose 0.71 mm: it sets the piston-to-head clearance.

The two brands

	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 region, and the group also has sites in Spain, the United States, Brazil and India. Its multi-layer gaskets fit certain car makers as original equipment, and its competition range is entirely designed and made in Italy.
	Cometic Gasket, Inc. was founded in 1989 in Concord, Ohio, and specialised in engine gaskets and sealing. It owes its reputation to made-to-measure gaskets, cut to the bore and thickness requested, and to an entirely American production from 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 gasket offered (86.75 mm for Athena, 87 and 88 mm for Cometic) 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-RPY-G02.

Important: the part numbers on this page only suit the K20C1 and K20C4 engines, and the Athena 338500FR is only listed for the K20C1: check your vehicle's engine code before ordering.

Why switch to a reinforced gasket?

When the original gasket can take no more, the reinforced gasket replaces it: under higher combustion pressure it holds its shape instead of being crushed.

A turbo, a supercharger or a raised compression ratio: in every case the head gasket is the first link to fail in the top end. A reinforced gasket prevents the leak and, above all, the head removal that follows, far costlier than the gasket.