Reinforced head gasket Toyota Land Cruiser 4.5 1FZ-FE

The Toyota engines covered

The Toyota 1FZ-FE petrol engine is a 4.5 litre inline six with 24 valves. In the table below it powers the Toyota Land Cruiser 80 (J8) and 100 (J1), the Land Cruiser (J7, JL7) and the Lexus LX 450. With a single cylinder head, the gasket is sold individually: one is needed per engine.

The original part numbers are 11115-66020, 11115-66030 and 11115-66031. Toyota publishes neither the bore, nor the thickness, nor the construction of this gasket, which is sized for standard combustion pressure: once that pressure rises, the clamping load relaxes, the head lifts away from the block and coolant passes into a cylinder.

Reinforced cylinder head gaskets

The gasket does not create the seal by itself: the fasteners clamping the head onto the block matter just as much. A composite gasket takes a permanent set beyond 100 N/mm², whereas the 301 stainless steel of the MLS and MLX withstands 517 N/mm², 5 times more, and returns to shape at every combustion. With the O-Ring, the stainless ring seals the combustion chamber on its own while the gasket body closes the water and oil circuits, with no machining of the block.

This page gathers the part numbers of two racing manufacturers, Athena and Cometic, in four constructions: the stainless-ring O-Ring and the multi-layer MLS for Athena, the multi-layer MLS and the chamber-stop MLX for Cometic. Bores range from 101.5 to 103 mm and thicknesses from 0.686 to 3.556 mm, enough to set the compression ratio without touching the pistons or the 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, one gasket per engine.

Technical specifications

The gasket volume is the space it leaves free above each cylinder: it adds to the combustion chamber and lowers the compression ratio by the same amount. Compare these volumes only between gaskets of the same bore.

Preparation and fitting

Before fitting, check the flatness of the head and the block with a straight edge, and have either one resurfaced if necessary. Apply no sealing paste: Athena and Cometic supply their gaskets already coated.

Technical guide

The four constructions offered

	O-Ring / Cut Ring Athena A steel carrier covered with asbestos-free aramid fibre, around which a stainless steel compression ring is crimped at each cylinder. The ring concentrates the clamping load on a thin band, exactly where the seal is decided, while a silicone bead protects the water and oil channels. It is the construction that resists the highest combustion pressures of the whole range.
	Athena MLS A stack of two to five AISI 301 stainless steel sheets, laser cut, stamped, then riveted. Around each cylinder, a folded sheet, the Gas Stopper, redirects the clamping load towards the combustion chamber, and raised beads isolate the water and oil circuits. A coating covers the outer faces: one layer withstands heat and takes up the small flaws of the block and head, a silicone layer stops the gasket sticking at removal. It is Athena's all-steel solution, from the prepared naturally aspirated engine to moderate boost; beyond that, the O-Ring remains the construction that carries the highest pressures.
	Cometic MLS Stainless steel sheets, stamped, stacked and riveted. The outer sheets show active beads around each cylinder and each fluid passage. The seal comes from a moderate clamping load and little bore distortion. It is the versatile choice, from the prepared naturally aspirated engine to light boost.
	MLX Cometic Embossed and riveted stainless steel sheets, one central sheet being folded into a stopper around the combustion chamber, beneath a high-temperature coating. The clamping load is concentrated where it is useful, without distorting the bore any further. It is the strongest all-steel gasket, meant for heavy boost; it is offered here in 101.5 mm and a single thickness of 1.016 mm.

Choosing bore and thickness

Gasket bore. The Athena O-Ring comes in 102.5 mm, the Athena MLS in 101.5 and 103 mm, and the Cometic MLS and MLX in 101.5 mm.

Thickness. Toyota does not state any 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 the manufacturer does not give the original thickness, use a dial gauge to read how far the pistons rise above the block's gasket face: that reading fixes the clearance left between piston and head, above all with the thinnest gasket.

The two brands

	Athena S.p.A. is an Italian company making gaskets and engine components. It is based in Alonte, in the Veneto, where its main plant also stands, with further sites in Spain, the United States, Brazil and India. Several car makers fit its multi-layer gaskets as original equipment, and the entire competition range is designed and manufactured in Italy.
	Cometic Gasket, Inc. is an American manufacturer of gaskets and sealing solutions for engines, created in 1989 in Concord, Ohio. It stands out for the made-to-order gasket, at the bore and thickness requested, built 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 bore of the gaskets offered (101.5 to 103 mm) 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: 11115-66020, 11115-66030, 11115-66031.

Important: the gaskets on this page are listed for the Land Cruiser 80 (J8), 100 (J1), (J7, JL7) and the Lexus LX 450, from 1992 to 2009. For any other vehicle, note the engine code before ordering.

Why switch to a reinforced gasket?

When the original gasket reaches its limit, the reinforced gasket takes over: at a higher combustion pressure it keeps its shape and does not settle.

A serious tune, added forced induction or a raised compression ratio all load the head gasket first, the first link to give way in the top end. A reinforced gasket avoids the leak and the head removal that follows, a job much dearer than the part itself.