Reinforced head gasket Nissan Stanza 1.8 CA18 SOHC 8v

The Nissan engines covered

The CA18 is a 1.8 litre four-cylinder petrol engine with eight valves and a single overhead camshaft (SOHC), fitted to the Nissan Stanza Hatchback (T11) listed in the compatibility table below. It has a single cylinder head and therefore takes one gasket.

Nissan publishes neither the part number, nor the bore, nor the thickness, nor the construction of this engine's original gasket. Sized for standard combustion pressure, an original gasket 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 Nissan.

This page brings together the part numbers of Cometic, the American maker of racing gaskets, in a single construction: the multi-layer steel MLS. Every gasket has an 85 mm bore and thicknesses from 0.69 to 3.56 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 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 every part number has an 85 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. Also clean the threaded holes in the block before fitting, then dry them.

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 numbers on this page are offered in this construction.

Choosing bore and thickness

Gasket bore. The Cometic MLS is offered in 85 mm (C4479), in that bore only.

Thickness. No thickness is published for this engine's 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 not published, use a dial gauge to measure how far the pistons stand above the block's gasket face, especially if you choose a thickness finer than that of the removed gasket: this reading gives the clearance left between piston and head. Take this measurement on all four pistons, at top dead centre.

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 CA18 of the Nissan Stanza.

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 Nissan 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: not published by the manufacturer.

Important: the part number on this page only suits the eight-valve CA18 (SOHC): check the engine code of your Nissan 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. On an eight-valve CA18, this applies above all to an engine whose power has been 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 CA18, it is mainly a tuned engine that strains the gasket.