Reinforced head gasket Nissan 370Z 350Z Infiniti G37 3.5 3.7 V6 VQ35HR VQ37VHR

The Nissan engines covered

The Nissan VQ35HR and VQ37VHR are the 3.5 and 3.7-litre 24-valve DOHC V6 petrol engines of the late 350Z, the 370Z, the Infiniti G37 and Q50; Cometic adds the second version of the VQ35DE to them. This page covers these engines: they take the same reinforced cylinder head gaskets, one for each cylinder bank.

On the VQ37VHR, the original gaskets carry part numbers 11044-EY02A to 11044-EY06A, 11044-JA11A, 11044-JA12A, 11044-JK21A, 11044-JK22A and 11044-9N00A to 11044-9N02A on the right, and the same numbers ending in B on the left. It is a multi-layer steel (MLS) gasket with a 96.1 mm bore, whose thickness Nissan does not publish. It is sized for standard combustion pressure: when that pressure rises, clamping load drops, the cylinder head lifts, and coolant passes into a cylinder.

Reinforced cylinder head gaskets

A cylinder head gasket does not create the seal on its own: it holds because the fasteners clamp the head against the block. A composite gasket is crushed for good beyond 100 N/mm² of admissible stress, whereas the 301 stainless steel of the MLS gaskets withstands 517 N/mm², 5 times more, and springs back at every combustion.

This page offers the part numbers from Cometic, a racing manufacturer, in MLS multi-layer steel construction. Gasket bores run from 97 to 100 mm, covering the standard block as well as the rebored block, and thicknesses from 0.58 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: a V6 needs a left-hand and a right-hand gasket.

Technical specifications

Gasket volume: the space the gasket leaves above each cylinder. It enlarges the combustion chamber, and the larger it is, the lower the compression ratio. Values compare with one another at identical gasket bore.

Preparation and fitting

Before fitting, check the flatness of the cylinder head and of the block with a straight edge and have them skimmed if necessary. These gaskets require no sealant: Cometic supplies them already coated.

Technical guide

The construction offered

Cometic MLS Several stamped and riveted stainless steel layers. The outer layers carry active beads around each cylinder and each fluid passage. Sealing is achieved with a moderate clamping load and limited bore distortion. This is the versatile choice, from a prepared naturally aspirated engine to light forced induction.

Choosing bore and thickness

Gasket bore. The Cometic MLS comes in 97, 99 and 100 mm.

Thickness. Nissan does not publish the thickness of the original gasket. A thicker gasket enlarges the combustion chamber and lowers the compression ratio; a thinner one reduces it and raises the ratio.

With a thickness finer than that of the removed gasket, measure piston protrusion above the block with a dial gauge: it is what determines the remaining clearance between piston and cylinder head.

The brand

Cometic Gasket, Inc. is an American manufacturer of engine gaskets and sealing solutions, founded in 1989 and based in Concord, Ohio. Its speciality is the made-to-order gasket, in the bore and thickness required. All its products are made in the United States, from 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 96.1 mm bore of the original gasket 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-EY02A to 11044-EY06A, 11044-JA11A, 11044-JA12A, 11044-JK21A, 11044-JK22A, 11044-9N00A to 11044-9N02A (right) ; same numbers ending in B (left).

Important: for the VQ35DE, Cometic distinguishes a first version, served by other part numbers (C4343 to C4381), and a second version, covered by this page. The VQ40DE is not covered by this page.

Why switch to a reinforced gasket?

A reinforced gasket holds where the standard one reaches its limit: at higher combustion pressure it keeps its shape instead of being crushed.

As soon as power goes up, turbo, supercharger or raised compression ratio, the head gasket becomes the weak link of the top end. Switching to a reinforced gasket is then not a comfort but a safeguard: it is what prevents the failure and the head removal that comes with it.