Reinforced cylinder head gasket Nissan RB20 2.0L

The Nissan engines covered

The Nissan petrol engines RB20E, RB20DE and RB20DET, of 2.0 litres, power the Skyline, Laurel, Cefiro, Stagea and Crew models detailed below, as well as the Holden Commodore.

Nissan publishes neither the part number of the original gasket of these engines, nor its bore, nor its thickness, nor its construction. That gasket is sized for standard pressure: when that climbs, clamping gives way, the cylinder head lifts and coolant reaches a cylinder.

Reinforced cylinder head gaskets

The head gasket does not seal by itself: the fasteners that clamp the head to the block weigh as much as it does. Beyond 100 N/mm², a composite gasket settles for good; the 301 stainless steel of MLS gaskets takes 517 N/mm², 5 times more, and regains its shape at every combustion.

This page gathers the part numbers of Cometic, an American maker of competition gaskets, in a single construction: the multi-layer steel MLS. The bores run from 80 to 83 mm and the thicknesses from 0.69 to 3.56 mm, enough to adjust the compression ratio without touching the pistons or the cylinder head. 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

The volume of a gasket is the empty space it leaves above each cylinder. That space adds to the combustion chamber and lowers the compression ratio, the more so as it is large. Compare these values only between gaskets of the same bore.

Preparation and fitting

Before fitting, check with a straightedge that the head and block faces are flat, and have them resurfaced if needed. Apply no sealing paste: Cometic gaskets are supplied coated.

Technical guide

The construction offered

MLS Cometic Stainless steel sheets, pressed and then joined by rivets. The outer sheets show active beads around each cylinder and each fluid passage. Moderate tightening is enough to seal, and the bore distorts very little. This versatile construction suits everything from the tuned naturally aspirated engine to moderate boost.

Choosing bore and thickness

Gasket bore. Cometic MLS is offered in 80 mm (C4495), in 81 mm (H2549SP1051S), in 81.5 mm (H2549SP9040S), in 82.5 mm (H2549SP2066S) and in 83 mm (H2549SPB051S, H2549SPB060S).

Thickness. Nissan gives no thickness for the original gasket of these engines. A thicker gasket enlarges the combustion chamber and lowers the compression ratio; a thinner one reduces it and raises the ratio.

If you settle on a thickness smaller than the original, start by measuring with a dial gauge how far the pistons stand above the block deck: that figure gives the clearance left between piston and head.

The brand

Cometic Gasket, Inc. is an American company, created in 1989 in Concord, Ohio, that produces engine gaskets and sealing solutions. It became known for the made-to-measure gasket, cut to the bore and thickness requested. All of its production stays in the United States, with American 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 original gasket, absent from Nissan's publications 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: part number not published by the manufacturer.

Important: the part numbers on this page match the Nissan RB20E, RB20DE and RB20DET engines: note your vehicle's engine code, then choose the bore, before ordering.

Why switch to a reinforced gasket?

Once the original gasket reaches its limit, the reinforced gasket takes the relay: under greater combustion pressure it holds its shape and does not flatten.

With a turbo, a supercharger or a raised compression ratio, the head works harder and the gasket becomes the most stressed part of the top end. A reinforced gasket rules out the gas or coolant leak, and the head removal that follows, with the vehicle off the road.