Reinforced cylinder head gasket BMW N62B44

The BMW engines covered

The BMW N62B44 is the V8 petrol engine, 4.4 litres and 32 valves, fitted to the BMW X5 4.4i (E53), 545i (E60 and E61 Touring), 645Ci (E63 coupé and E64 convertible) and 745i and 745Li (E65, E66 and E67) listed below.

This original gasket carries the part number 11 12 7 513 944. It is a multi-layer steel (MLS) gasket with a 93 mm bore and a thickness of 0.75 mm; its repair size, 11 12 7 513 945, measures 1.05 mm, that is 0.30 mm more. The engine takes two of them, one per cylinder bank. It is calibrated for standard combustion pressure: when that pressure rises, the clamping load relaxes, the cylinder head lifts and coolant finds its way into a cylinder.

Reinforced cylinder head gaskets

The seal does not come from the gasket alone: it depends on the fasteners, which clamp the cylinder head against the block. Above 100 N/mm² of allowable stress, a composite gasket is crushed for good, whereas the 301 stainless steel of the MLS withstands 517 N/mm², 5 times more, and springs back to shape at every combustion.

This page brings together the Cometic part numbers, an American maker of competition gaskets, in a single construction: MLS, multi-layer steel. Every part number has a 94 mm bore, 1 mm larger than the original gasket, and the thicknesses run 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; the engine takes two gaskets, one per cylinder bank, so order two.

Technical specifications

The gasket volume is the space it leaves above each cylinder. It adds to the combustion chamber, so the larger it is, the lower the compression ratio. Compare these volumes only between gaskets of the same bore.

Preparation and fitting

Before fitting, check with a straightedge that the cylinder head and block faces are flat, and have them resurfaced if needed. No sealant is required: Cometic supplies these gaskets already coated.

Technical guide

The construction offered

Cometic MLS A stack of stamped stainless steel sheets, held together by rivets. The outer sheets carry active beads around each cylinder and each fluid passage. A moderate clamping load is enough to seal, and the bore distorts very little. It is the all-round solution, from the tuned naturally aspirated engine to moderate boost.

Choosing bore and thickness

Gasket bore. The Cometic MLS comes in 94 mm (C4374), and in that bore only.

Thickness. The original gasket is 0.75 mm thick, and 1.05 mm in repair size (+0.30 mm). A thicker gasket enlarges the combustion chamber and lowers the compression ratio; a thinner one reduces it and raises the ratio.

When the thickness you pick is below the original, use a dial gauge to read how far the pistons stand proud of the block: that figure sets the clearance left between piston and cylinder head.

The brand

Cometic Gasket, Inc., founded in 1989 in Concord, Ohio, is an American company specialising in engine gaskets and sealing solutions. It made its name with the made-to-order gasket, supplied in the bore and thickness requested. All its production stays in the United States, using 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 93 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: 11 12 7 513 944 in standard size, 11 12 7 513 945 in repair size (two gaskets per engine, one per cylinder bank).

Important: this engine takes two cylinder head gaskets, one per cylinder bank: order two of the chosen part number. The part numbers on this page only suit the N62B44: check your vehicle's engine code before ordering.

Why switch to a reinforced gasket?

Once the original gasket has reached its limit, the reinforced version keeps sealing: as combustion pressure climbs, it holds its shape where a standard gasket would be crushed.

When power goes up, through a supercharger, a turbo or a raised compression ratio, the head gasket is the first part of the top end to give way. Choosing a reinforced gasket means putting reliability before comfort: you avoid the failure, and the cylinder head removal that follows.