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BY REFERENCE COMETIC - Reinforced cylinder head gaskets
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BY REFERENCE COMETIC - Reinforced cylinder head gaskets
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Reinforced Cometic MLX and Athena MLS head gaskets, sold individually: one gasket per cylinder bank, so two per engine.
The FA20, listed under the codes FA20, FA20D and 4U-GSE, is a 2.0 litre, 16-valve petrol flat-four fitted to the Toyota GT 86 (ZN6), detailed in the table below. It has two cylinder heads, so one gasket is needed per cylinder bank.
Two original part numbers are on record: 11044-AA810 for the right bank and 10944-AA100 for the left bank. The manufacturer publishes neither their bore, nor their thickness, nor their construction. Sized for standard combustion pressure, these gaskets give way once it is exceeded: the clamping load drops, the head opens up and coolant reaches the cylinder.
Sealing does not rest on the gasket alone: the fasteners that clamp each head onto the block provide half of it. A fibre gasket settles for good beyond 100 N/mm² of stress, whereas the 301 stainless steel of MLS and MLX gaskets withstands 517 N/mm², 5 times more, and springs back at every combustion.
This page brings together eighteen part numbers from two competition makers: fourteen Cometic (United States) MLX gaskets, 89.5 mm bore, in seven thicknesses from 0.81 to 1.32 mm, and four Athena (Italy) MLS gaskets, 89.5 mm bore, in 0.80 and 0.95 mm. Each part number serves one bank only and is sold individually: order one for the left and one for the right, of the same thickness.
| Gasket bore | Thickness | Gasket volume | Gasket type OEM not specified | Brand | Part number OEM 11044-AA810 | 10944-AA100 |
| 89.5 mm | 0.80 mm | 5.03 | MLS right bank | Athena | 338489R |
| 89.5 mm | 0.80 mm | 5.03 | MLS left bank | Athena | 338490R |
| 89.5 mm | 0.81 mm | 5.10 | MLX right bank | Cometic | C4588-032 |
| 89.5 mm | 0.81 mm | 5.10 | MLX left bank | Cometic | C4589-032 |
| 89.5 mm | 0.91 mm | 5.73 | MLX right bank | Cometic | C4588-036 |
| 89.5 mm | 0.91 mm | 5.73 | MLX left bank | Cometic | C4589-036 |
| 89.5 mm | 0.95 mm | 5.98 | MLS right bank | Athena | 338491R |
| 89.5 mm | 0.95 mm | 5.98 | MLS left bank | Athena | 338492R |
| 89.5 mm | 1.02 mm | 6.42 | MLX right bank | Cometic | C4588-040 |
| 89.5 mm | 1.02 mm | 6.42 | MLX left bank | Cometic | C4589-040 |
| 89.5 mm | 1.07 mm | 6.73 | MLX right bank | Cometic | C4588-042 |
| 89.5 mm | 1.07 mm | 6.73 | MLX left bank | Cometic | C4589-042 |
| 89.5 mm | 1.22 mm | 7.68 | MLX right bank | Cometic | C4588-048 |
| 89.5 mm | 1.22 mm | 7.68 | MLX left bank | Cometic | C4589-048 |
| 89.5 mm | 1.27 mm | 7.99 | MLX right bank | Cometic | C4588-050 |
| 89.5 mm | 1.27 mm | 7.99 | MLX left bank | Cometic | C4589-050 |
| 89.5 mm | 1.32 mm | 8.30 | MLX right bank | Cometic | C4588-052 |
| 89.5 mm | 1.32 mm | 8.30 | MLX left bank | Cometic | C4589-052 |
A gasket's volume is the space it leaves free above each cylinder. It adds to the combustion chamber and lowers the compression ratio: only gaskets of the same bore can be compared.
| Fasteners | Engines | Tightening torque |
| Original cylinder head bolts 11095AA160 | FA20, FA20D, 4U-GSE | not published by the manufacturer |
Before fitting, check the flatness of both heads and of the block with a straight edge, and have any warped surface machined. Cometic and Athena gaskets arrive already coated: add no sealing paste.
 | Athena MLS Athena MLS Two to five AISI 301 stainless steel sheets, laser cut, stamped and riveted. A folded sheet surrounds each cylinder as a Gas Stopper and carries the clamping load toward the combustion chamber, while embossings seal off the water and oil passages. A heat coating fills the flaws of block and head, and a silicone layer stops the gasket from sticking at removal. It is Athena's all-steel solution, from the tuned naturally aspirated engine to moderate boost. Each part number is inspected before dispatch. |
 | Cometic MLX Several stamped, riveted stainless steel sheets, the centre one folded into a stopper around each combustion chamber, under a heat-resistant coating. The clamping load concentrates there without distorting the bore. It is the strongest of the all-steel constructions in the range, meant for heavily stressed engines. |
Gasket bore. The Cometic MLX and the Athena MLS come in a single bore, 89.5 mm (C4588, C4589 and 338489R to 338492R).
Thickness. No thickness is given by the manufacturer for the original gaskets. A thicker gasket enlarges the combustion chamber and lowers the compression ratio; a thinner one reduces it and raises the ratio.
| Your goal | Thickness to choose |
| Keep the original compression ratio | Original thickness not published: measure the removed gasket and pick the closest of the nine thicknesses offered, from 0.80 to 1.32 mm |
| Skimmed cylinder head, make up the lost height | From 0.80 to 1.32 mm, start from the thickness of the removed gasket, plus the material taken off when resurfacing |
| Forced induction build, lower the ratio | A thicker gasket, up to 1.32 mm, to lower the compression ratio, if the removed gasket is thinner |
| Naturally aspirated build, raise the ratio | A thinner gasket, down to 0.80 mm, to raise the compression ratio, if the removed gasket is thicker |
As the original thickness is not published, read with a dial gauge how far the pistons stand proud of the block's gasket face before choosing: this figure gives the clearance left between piston and head, above all with a 0.80 mm gasket.
 | Athena S.p.A. is an Italian maker of gaskets and engine parts whose head office and main plant are in Alonte, in the Veneto. The group also has sites in Spain, the United States, Brazil and India, and its competition range is designed and made entirely in Italy. Its multilayer gaskets are also fitted by manufacturers as original equipment. |
 | Cometic Gasket, Inc. is an American company based in Concord, Ohio, founded in 1989, that designs gaskets and sealing solutions for engines. It became known for the made-to-measure gasket, cut to the bore and thickness wanted and made in the United States from American raw materials. |
| Criterion | Original gaskets 11044-AA810 and 10944-AA100 | Reinforced gaskets |
| Construction | Construction not specified by the manufacturer | Multilayer stainless steel (MLX and MLS) |
| Gasket bore | not published by the manufacturer | 89.5 mm |
| Thicknesses available | not published by the manufacturer | 0.80 to 1.32 mm, nine values |
| Compression ratio adjustment | None | Through the thickness chosen |
| Resistance to overpressure | Limited to standard output | Designed for forced induction |
| Model | Engine code | Power | Years |
| Toyota GT 86 Coupé (ZN6) 2.0 | FA20 | not published | 2012- |
| Subaru, moteur 2.0 16V | FA20 | not published | - |
| Toyota, moteur 2.0 16V | FA20D | not published | - |
| Toyota, moteur 2.0 16V | 4U-GSE | not published | - |
OEM part number: 11044-AA810 (right bank) and 10944-AA100 (left bank).
Important: the part numbers on this page suit the FA20, FA20D and 4U-GSE engines: each engine needs two gaskets, one per bank. Take C4589, 338490R or 338492R for the left, C4588, 338489R or 338491R for the right.
When the original gasket reaches its limit, the reinforced gasket takes over: under high combustion pressure it keeps its shape and does not settle.
On this flat-four, a turbocharger or a higher compression ratio makes the head gasket the first weak link. The reinforced gasket prevents the leak, whereas removing two cylinder heads costs far more than the part. It is wiser to prevent it than to rework the top end twice.
