Reinforced head gasket Honda Civic VIII IX FR-V 1.8 R18A1 R18A2 R18Z1 R18Z4

The Honda engines covered

The R18A1, R18A2, R18Z1 and R18Z4 are naturally aspirated 1.8 litre four-cylinder petrol engines, fitted to the Honda Civic VIII and IX and FR-V listed in the compatibility table below. Each has a single cylinder head and therefore takes one gasket.

The original gasket carries part number 12251-R60-U01 on the R18A1, R18A2, R18Z1 and R18Z4. Honda publishes neither its bore, nor its thickness, nor its construction. Sized for standard combustion pressure, it reaches its limit as soon as that pressure rises: clamping load drops, the head lifts and coolant finds its way into a cylinder.

Reinforced cylinder head gaskets

The gasket's hold also depends on the fasteners that clamp the head onto the block. A composite gasket is permanently crushed beyond 100 N/mm²; the 301 stainless steel of an MLS gasket withstands 517 N/mm², 5 times more, and returns to shape at every combustion. Replace any head bolt that is stretched or damaged. For this engine, follow the tightening sequence and torque specified by Honda.

This page presents part number C14170-030 from Cometic, the American maker of racing gaskets, in a single construction: the multi-layer steel MLS. Its bore is 81.5 mm and its thickness 0.76 mm. As a rule, the gasket bore chosen is at least 0.5 mm larger than the actual cylinder bore. It is sold individually, one gasket per engine.

Technical specifications

A gasket's volume is the free space it leaves above each cylinder. It adds to the combustion chamber and lowers the compression ratio: the thicker the gasket, the larger that volume. Here the single part number has a 81.5 mm bore.

Preparation and fitting

Before refitting, check the flatness of head and block with a straight edge and have the faces ground if necessary. The Cometic gasket comes pre-coated: do not apply any sealant. This check matters most if the gasket face has already been skimmed or shows traces of a leak.

Technical guide

The construction offered

Cometic MLS A stack of stamped and riveted stainless steel sheets. The outer sheets carry active beads that surround every cylinder and every fluid passage. Moderate clamping is enough to seal and the bore stays stable: a versatile construction, from the tuned naturally aspirated engine to moderate boost. The part number C14170-030 on this page is offered in this construction.

Choosing bore and thickness

Gasket bore. The Cometic MLS C14170-030 comes in 81.5 mm, in that bore only.

Thickness. No thickness is published for the original gasket 12251-R60-U01. 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 not published, use a dial gauge to measure how far the pistons stand above the block's gasket face, especially if the removed gasket is thicker than 0.76 mm: this reading gives the clearance left between piston and head.

The brand

Cometic Gasket, Inc. is an American company created in 1989 and based in Concord, Ohio, specialised in engine gaskets and sealing solutions. It made its name with the custom gasket, made to the bore and thickness required and manufactured in the United States. Its MLS range also covers the R18 of the Honda Civic.

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 original gasket, a dimension Honda does not publish 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-R60-U01 (R18A1, R18A2, R18Z1, R18Z4).

Important: the part number on this page only suits the R18A1, R18A2, R18Z1 and R18Z4 engines: check the engine code of your Honda before ordering.

Why switch to a reinforced gasket?

When the original gasket reaches its limit, the reinforced one takes over: under stronger combustion pressure it keeps its shape instead of crushing. This applies to an engine whose compression ratio or power is raised.

Fitting a bigger turbo, raising boost pressure or increasing the compression ratio puts the head gasket under strain first, as the weak link of the top end. A reinforced gasket prevents the leak, and with it a head removal far more expensive than the part itself. On a naturally aspirated 1.8 litre such as the R18A1, it is mainly a tuned engine that strains the gasket.