Reinforced head gasket Nissan VG30DE VG30DETT

The Nissan engines covered

The VG30DE and VG30DETT are 3.0-litre Nissan petrol engines with six cylinders in a V and 24 valves: the VG30DE is naturally aspirated, the VG30DETT is fed by two turbochargers. They power the Nissan 300ZX (Z32), Maxima, Cedric, Cima and Gloria models in the compatibility table below. A V6 needs a left and a right gasket: allow for two gaskets per engine.

The original gasket of these engines carries part number 11044-40P00. Nissan publishes neither its bore, nor its thickness, nor its construction. It is sized for the standard combustion pressure; as soon as it rises, the clamping load relaxes, the head lifts and coolant seeps into a cylinder.

Reinforced cylinder head gaskets

The gasket does not seal alone: the fasteners that press the head onto the block count just as much. Above 100 N/mm² of stress a composite gasket settles for good; the 301 stainless steel of MLS gaskets holds up to 517 N/mm², 5 times more, and recovers its shape with 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 range from 88 to 90 mm and thicknesses from 0.69 to 3.56 mm, enough to set the compression ratio to suit the build. As the engine is a V6, each cylinder head takes its own gasket: choose the bore, thickness and construction you want, and order for both banks of cylinders.

Technical specifications

The gasket volume is the free space it leaves above each piston: it adds to the combustion chamber and lowers the compression ratio. Compare only gaskets of the same bore: here they differ between the Cometic part numbers, at 88 and 90 mm, and the Athena, at 89 mm.

Preparation and fitting

Before fitting, check the flatness of the head and the block with a straightedge and have any distorted surface machined. Cometic and Athena supply gaskets that are already coated: do not add sealing paste, it would bring nothing and would upset the clamping load.

Technical guide

The two constructions offered

Athena O-Ring / Cut Ring A steel sheet lined with asbestos-free aramid fibre, with a stainless steel compression ring around each cylinder. The ring concentrates the clamping load exactly where the seal is made, and a silicone bead protects the water and oil passages. This construction withstands the highest pressures. It suits heavily boosted engines, but calls for very flat mating faces and a careful, even tightening of the head.

Cometic MLS Stainless steel sheets, stamped, stacked and then riveted. The outer sheets have active beads around every cylinder and every fluid passage. A moderate clamping load is enough to seal and the bore distorts little: a versatile construction, from the tuned naturally aspirated engine to moderate forced induction.

Choosing bore and thickness

Gasket bore. The Cometic MLS comes in 88 mm (C4346, from 0.69 to 3.56 mm) and in 90 mm (C4347, from 0.69 to 3.56 mm); the Athena O-Ring 330168R comes in 89 mm.

Thickness. Nissan quotes no thickness 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.

As no original thickness is published, use a dial gauge to measure how far the pistons stand proud of the block deck before ordering, especially for a gasket thinner than the one removed: this figure gives the real clearance between piston and head.

The two brands

	Athena S.p.A. is an Italian maker of gaskets and engine components; its head office and main factory are in Alonte, in the Veneto, and the group also produces in Spain, the United States, Brazil and India. Car manufacturers fit its multi-layer gaskets as original equipment, and the whole competition range is designed and built in Italy.
	Cometic Gasket, Inc. is an American maker of gaskets and sealing solutions for engines, founded in 1989 and based in Concord, Ohio. Its speciality is the made-to-measure gasket, cut to the bore and thickness ordered and made 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 88, 89 and 90 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: 11044-40P00.

Important: these part numbers are for the VG30DE and VG30DETT engines: check your vehicle's engine code before ordering, then choose the bore, thickness and construction you want.

Why switch to a reinforced gasket?

When the original gasket reaches its limit, the reinforced gasket takes over: under a higher combustion pressure the steel MLS does not crush and keeps its shape, and the O-Ring keeps the seal thanks to its compression ring.

As soon as an engine gets a turbo or a supercharger, or its compression ratio goes up, the head gasket becomes the weak point of the top end. A reinforced gasket avoids the leak, and the head removal that follows, a far costlier job: it is better to fit one before the build than after the first breakdown.