Reinforced head gasket Nissan RB30E RB30ET RB30S

The Nissan engines covered

The RB30E, RB30ET and RB30S are 3.0-litre Nissan petrol engines with six cylinders in line and 12 valves: the RB30E is fuel-injected, the RB30S is carburetted and the RB30ET is fed by a turbocharger. They power the Nissan Skyline (R31) and Patrol (K260, W260, Y60) as well as the Holden Commodore VL Turbo in the compatibility table below. An in-line six has a single cylinder head: allow for just one gasket per engine.

The original gasket of these engines carries part number 11044-67S02. Nissan publishes neither its bore, nor its thickness, nor its construction. It is sized for standard pressures; when they rise, the clamping load drops, the head lifts slightly off the block and coolant seeps into a cylinder.

Reinforced cylinder head gaskets

How well the gasket holds also depends on the fasteners, which press the head against the block. A composite gasket takes a permanent set beyond 100 N/mm²; the 301 stainless steel of MLS gaskets withstands up to 517 N/mm², 5 times more, and springs back after every combustion.

This page groups 37 part numbers from two competition manufacturers, Cometic (United States) and Athena (Italy): 36 in MLS, multi-layer steel, and one O-Ring. Bores are 86 and 87 mm and thicknesses run from 0.69 to 3.56 mm, enough to set the compression ratio to suit the build. As the engine has a single head, one gasket is enough: choose the bore, thickness and construction you want.

Technical specifications

Gasket volume is the space it leaves above each piston. That space adds to the combustion chamber volume and lowers the compression ratio. Only compare gaskets of the same bore: here, 86 and 87 mm for the Cometic part numbers and 87 mm for the Athena.

Preparation and fitting

Before fitting, lay a straightedge across the head and the block deck, and have anything out of true machined. Cometic and Athena gaskets arrive pre-coated: do not add sealant, as it does nothing useful and upsets the clamping load.

Technical guide

The two constructions offered

Athena O-Ring / Cut Ring A steel plate faced with asbestos-free aramid fibre, with a stainless compression ring around each cylinder. The ring brings the clamping load exactly where sealing is needed, and a silicone bead protects the water and oil circuits. This construction takes the highest pressures and suits heavily boosted engines, provided the mating faces are flat and the head is tightened with care.

Cometic MLS Several stainless steel sheets, stamped then riveted into a single stack. The outer sheets carry active beads around each cylinder and each fluid passage. Sealing comes with a moderate clamping torque and the bore moves little: a versatile construction, from the tuned naturally aspirated engine to the medium-boost turbo.

Choosing bore and thickness

Gasket bore. The Cometic MLS comes in 86 mm (C4322, from 0.69 to 3.56 mm) and in 87 mm (C4323, from 0.69 to 3.56 mm); the Athena O-Ring 330153R comes in 87 mm.

Thickness. Nissan gives no thickness figure for its standard gasket. A thicker gasket enlarges the combustion chamber and lowers the compression ratio; a thinner one reduces it and raises the ratio.

With no published original thickness, measure with a dial gauge how high the pistons rise above the block deck before ordering, especially if you want a gasket thinner than the one removed: it sets the clearance left between piston and head.

The two brands

	Athena S.p.A. is an Italian maker of gaskets and engine parts, with its head office and main plant in Alonte, in the Veneto. The group also has sites in Spain, the United States, Brazil and India. Some car makers fit its multi-layer gaskets as original equipment, and the whole competition range is designed and produced in Italy.
	Cometic Gasket, Inc. is an American company specialising in gaskets and engine sealing, founded in 1989 and based in Concord, Ohio. It cuts each gasket to order, at the bore and thickness required, and makes it entirely in the United States 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 86 and 87 mm bores 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: 11044-67S02.

Important: these part numbers are for the RB30E, RB30ET and RB30S engines: check your vehicle's engine code before ordering, then choose the bore, thickness and construction you want.

Why switch to a reinforced gasket?

Where the original gasket gives up, the reinforced one holds: at higher combustion pressure the steel MLS keeps its shape without crushing, and the O-Ring keeps sealing thanks to its compression ring.

With a turbo, a supercharger or a raised compression ratio, the head gasket is the first part to give way in the top end. Choosing a reinforced one from the start avoids the leak and the far costlier head removal that follows: better to invest before the build than after the failure. On the RB30ET, already turbocharged from the factory, this is even more true.