Reinforced head gasket Land Rover Range Rover II 3.9 4.0 4.6 V8 42D 46D

The Rover engines covered

The petrol V8 engines of 3.9, 4.0 and 4.6 litres, codes 42D and 46D, power the Range Rover II (P38A), listed below.

The original head gaskets listed for these engines carry the part numbers ERR 7217, LVB 50030 and LVB500030. The manufacturer does not release their bore, thickness or construction. They are sized for standard combustion pressure: when it climbs, the clamping force relaxes, the cylinder head lifts off the block and coolant leaks into a cylinder.

Reinforced cylinder head gaskets

The gasket does not seal on its own: the fasteners that pull the cylinder head down onto the block provide half of the sealing. A composite gasket is permanently crushed from 100 N/mm² of stress, whereas the 301 stainless steel of MLS gaskets withstands 517 N/mm², 5 times more, and recovers its shape on every combustion.

This page groups the part numbers from the American maker Cometic, a specialist in competition gaskets, in a single construction: MLS. Three bores are offered, 94, 96 and 96.5 mm: the first two in 18 thicknesses from 0.69 to 3.56 mm, the 96.5 mm in 5 thicknesses from 1.52 to 3.05 mm, so the compression ratio can be set without touching the pistons or the cylinder head. Each part number is sold individually; a V8 requires two, one for each cylinder bank.

Technical specifications

A gasket's volume is the space it provides above each cylinder. That space adds to the combustion chamber and lowers the compression ratio; only gaskets of the same bore can be compared with each other.

Preparation and fitting

Before fitting, check with a straight edge that the cylinder head and block are flat, and have them machined if needed. Cometic delivers its gaskets pre-coated: apply no sealing paste.

Technical guide

The construction offered

Cometic MLS Stainless steel sheets, stamped, stacked and riveted together. The outer sheets show active beads around each cylinder and each coolant passage. A moderate tightening is enough to seal, with little bore distortion. It is the versatile choice, from the tuned naturally aspirated engine to moderate boost.

Choosing bore and thickness

Gasket bore. The Cometic MLS comes in 94 mm, 96 mm and 96.5 mm, with no other bore.

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

As no original thickness is published, use a dial gauge to read how far the pistons stand proud of the block face before moving to a gasket thinner than the removed one: this figure gives the clearance left between piston and cylinder head.

The brand

Cometic Gasket, Inc. is an American company set up in 1989 in Concord, Ohio, that designs gaskets and sealing components for engines. Its reputation comes from the made-to-measure gasket, produced to the bore and thickness required from American 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 94 mm, 96 mm or 96.5 mm bore of the gaskets offered 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: ERR 7217, LVB 50030 and LVB500030.

Important: the part numbers on this page suit the engines 42D and 46D: check your vehicle's engine code, then choose the gasket bore according to that of your cylinders before ordering.

Why switch to a reinforced gasket?

When the original gasket reaches its limit, the reinforced one takes over: under greater combustion pressure it does not sag and holds its shape.

With a turbo, a supercharger or a higher compression ratio, the head gasket becomes the first weak point of the top end. A reinforced gasket prevents the leak, and the head removal that follows costs much more than the gasket.