Reinforced cylinder head gasket Honda NSX C30A1 C32B1 95 mm

The Honda engines covered

The V6 petrol engine of 3.0 litres with 24 valves and VTEC valve timing (C30A) powers the Honda NSX (NA1); the version of 3.2 litres, C32B, powers the NSX from 1997. The Cometic part numbers on this page are given by the maker for the C30A1 and C32B1 engines, detailed below.

Honda publishes no part number for the original gasket of these engines, nor its bore, thickness or construction. This standard gasket is sized for the original pressure: when it rises, the clamping load relaxes, the head lifts off the block and coolant works its way into a cylinder.

Reinforced cylinder head gaskets

The head gasket does not seal by itself: the fasteners clamping the Honda head to the block matter as much as it does. Beyond 100 N/mm², a composite gasket takes a permanent set; the 301 stainless steel of MLS gaskets withstands up to 517 N/mm², 5 times more, and recovers its shape at each combustion.

This page groups the part numbers of Cometic, an American maker of competition gaskets, in a single construction: MLS, a multi-layer steel design. A single bore is offered, 95 mm, with 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 singly and covers one cylinder bank only: you need one for the right bank and one for the left.

Technical specifications

Gasket volume is the void it leaves above each Honda cylinder. It adds to the combustion chamber and lowers the compression ratio, all the more as it is larger. Only compare these values between gaskets of the same bore.

Preparation and fitting

Before assembly, use a straight edge to check that the Honda head and block faces are flat, and have those that need it resurfaced. Do not apply any gasket sealant: Cometic gaskets are supplied already coated.

Technical guide

The construction offered

MLS Cometic Stamped stainless steel layers, joined with rivets. The outer layers have active beads around every Honda cylinder and every fluid passage. Moderate torque is enough to seal and the bore barely distorts. This versatile construction suits everything from the prepared naturally aspirated engine to moderate boost.

Choosing bore and thickness

Gasket bore. Cometic MLS is offered in a 95 mm bore (C4277).

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

Should you pick a thickness below the original, first use a dial gauge to measure how much the pistons stand proud of the Honda block face: that figure gives the clearance left between piston and head.

The brand

Cometic Gasket, Inc., founded in 1989 in Concord, Ohio, is a US company that designs gaskets and sealing solutions for engines. It made its name with the made-to-measure gasket, cut to the bore and thickness needed. All of its manufacturing remains 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 standard gasket, a value Honda does not give 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 are intended for the Honda C30A1 and C32B1 engines: identify the engine code of your vehicle and check the bore before placing your order.

Why switch to a reinforced gasket?

Once the original gasket is no longer sufficient, the reinforced one takes over: under higher combustion pressure it keeps its shape and is not crushed.

Once a turbo, a supercharger or a raised compression ratio is involved, the Honda head carries a heavier load and the gasket becomes the most stressed part of the top end. A reinforced gasket prevents gas or coolant leaks and the head removal that would follow.