Reinforced cylinder head gasket Toyota Lexus V8 UR 1UR 2UR 3UR

The Toyota engines covered

The Toyota UR family V8 engines, of 4.6 litres (1UR-FE, 1UR-FSE), 5.0 litres (2UR-FSE, 2UR-GSE) and 5.7 litres (3UR-FE, 3UR-FBE), power Lexus models (GS, GX, IS, LC, LS, LX, RC) and Toyota models (Century, Crown, Land Cruiser 200, Sequoia, Tundra), detailed below.

Toyota gives the part numbers 11115-38020 and 11115-38021 for the original gasket of these engines, but publishes neither its bore, nor its thickness, nor its construction. Each bank of four cylinders has its own gasket, sized for the standard combustion pressure: once it rises, the clamping load fades, the head lifts slightly and coolant reaches a cylinder.

Reinforced cylinder head gaskets

Sealing does not rest on the gasket alone: the fasteners that clamp the head to the block count just as much. The stainless steel of an MLS gasket keeps its strength under high pressure, where a conventional gasket flattens.

This page presents the two part numbers of the American maker Cometic, a specialist in racing gaskets, in a single construction: MLS, a stainless steel multilayer. The V8 needs two gaskets, one per bank: C4993-034 for the left bank and C4994-034 for the right bank. Their bore is 97 mm and their thickness 0.86 mm. Each part number is sold individually.

Technical specifications

Gasket volume is the empty space it leaves above each cylinder: it adds to the combustion chamber and lowers the compression ratio. Two gaskets can only be compared at the same bore.

Preparation and fitting

Before fitting, check the flatness of the head and of the block with a straightedge, and have them resurfaced if needed. Cometic checks every MLS gasket before shipping and none of them needs sealing paste.

Technical guide

The construction offered

Cometic MLS Several stamped, riveted stainless steel sheets, stacked together. The outer sheets show active beads around each cylinder and each fluid passage. The gasket seals with a moderate clamping load and distorts the bore little. It suits the prepared naturally aspirated engine up to moderate boost.

Choosing bore and thickness

Gasket bore. The Cometic MLS gaskets exist in 97 mm (C4993-034 for the left bank and C4994-034 for the right bank), with no other bore.

Thickness. The manufacturer publishes no thickness for the original gasket, so the figure measured on the removed gasket is the reference. A thicker gasket enlarges the combustion chamber and lowers the compression ratio; a thinner one reduces it and raises the ratio.

With no original thickness published, use a dial gauge to read how far the pistons stand above the block face, above all if the removed gasket is thicker than 0.86 mm: this figure gives the clearance left between piston and head.

The brand

Founded in 1989 and based in Concord, Ohio, Cometic Gasket, Inc. makes gaskets and sealing solutions for engines. Its speciality is the made-to-order gasket, produced to the bore and thickness requested, entirely 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 97 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: 11115-38020 and 11115-38021.

Important: C4993-034 (left bank) and C4994-034 (right bank) suit the UR engines of 4.6, 5.0 and 5.7 litres listed on this page: each engine needs both part numbers.

Why switch to a reinforced gasket?

When the original gasket reaches its limit, the reinforced gasket replaces it: under higher combustion pressure it holds its shape instead of being crushed.

On an engine worked close to its limits, whether turbocharged, supercharged or with a higher compression ratio, the head gasket is often the first part to give way. A reinforced gasket prevents the leak and costs far less than the head removal that would follow.