Reinforced head gasket Nissan 2.5 RB25DE RB25DET

The Nissan engines covered

The RB25DE and RB25DET are 2.5 litre petrol engines with twenty-four valves; the RB25DET is the turbocharged version. They power the Nissan Skyline (R32, R33, R34), Laurel (C33, C34, C35), Stagea (WC34), Cefiro I (A31), Cedric X and Gloria XI (Y34) models in the compatibility table below, and each takes a single cylinder head gasket.

The original gasket of the RB25DET carries part number 11044-75T02. Nissan 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

Sealing does not depend on the gasket alone: it also rests on the fasteners that clamp the head on the block. A composite gasket sets permanently beyond 100 N/mm² of stress, whereas the 301 stainless steel of MLS gaskets holds up to 517 N/mm², 5 times more, and springs back with every combustion.

This page brings together three part numbers from two competition makers, Athena (Italy) and Cometic (United States), all in multi-layer steel MLS construction. Athena offers two thicknesses, 1.3 mm (338144R) and 1.5 mm (338414R), with an 87 mm bore; Cometic offers 1.5 mm (H2025SPA059PR) with an 86.5 mm bore. The engine takes only one gasket: order a single part number, according to the 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 Athena and the Cometic here do not share one.

Preparation and fitting

Before fitting, run a straight edge over the cylinder head and block to check their flatness, and have them resurfaced if necessary. Athena and Cometic supply their gaskets already coated: no sealing paste is needed.

Technical guide

The two constructions offered

Athena MLS Athena MLS A stack of two to five AISI 301 stainless steel layers, laser cut, stamped and riveted. A folded layer wraps each cylinder and forms a Gas Stopper that carries the clamping load to the combustion chamber, while beads seal off the water and oil circuits. Both outer faces carry a coating: one layer resists high temperatures and makes up for small flaws in the block and head, a silicone layer stops the gasket sticking on removal. It is Athena's all-steel solution, from the prepared naturally aspirated engine to moderate boost.

Cometic MLS A stack of stamped, riveted stainless steel sheets. The outer sheets show active beads around each cylinder and each fluid passage. Moderate tightening is enough to seal and the bore barely deforms: a versatile construction, from the prepared naturally aspirated engine to moderate boost.

Choosing bore and thickness

Gasket bore. The Athena MLS is available here in 87 mm (338144R and 338414R) and the Cometic MLS in 86.5 mm (H2025SPA059PR).

Thickness. Nissan 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 Nissan 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 1.3 mm: it sets the piston-to-head clearance.

The two brands

	Athena S.p.A. is an Italian maker of gaskets and engine parts. Its head office and main plant are in Alonte, in the Veneto, and the group also has sites in Spain, the United States, Brazil and India. Car makers use its multi-layer gaskets as original equipment, and its entire competition range is designed and made in Italy.
	Cometic Gasket, Inc. is an American company set up in 1989 in Concord, Ohio, specialising in engine gaskets and sealing. Its reputation rests on the made-to-measure gasket, cut to the bore and thickness required, and on all-American manufacturing from domestic 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 (87 mm for Athena, 86.5 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: 11044-75T02 (RB25DET).

Important: the part numbers on this page only suit the RB25DE and RB25DET engines: check your vehicle's engine code before ordering.

Why switch to a reinforced gasket?

When the original gasket is outmatched, the reinforced gasket takes over: even under higher combustion pressure it keeps its shape instead of being crushed.

As soon as you add a turbo or a supercharger, or raise the compression ratio, the head gasket is the first part of the top end to give up. A reinforced gasket avoids the leak and the far costlier head removal that follows.