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2.0 16v - F20C
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2.0 16v - F20C
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Reinforced Athena and Cometic head gasket, in MLS for F20C and F22C1. Sold individually.
The Honda F20C is the 2.0-litre 16-valve DOHC VTEC inline four-cylinder petrol engine of the Honda S2000; the F22C1 is its 2.2-litre version. This page covers the F20C1, F20C2 and F22C1: these engines take the same reinforced cylinder head gaskets.
The original gasket carries part number 12251-PCX-004. It is a multi-layer steel (MLS) gasket with a 88 mm bore, whose thickness Honda does not publish. It is sized for standard combustion pressure: when that pressure rises, clamping load drops, the cylinder head lifts, and coolant passes into a cylinder.
A cylinder head gasket does not create the seal on its own: it holds because the fasteners clamp the head against the block. A composite gasket is crushed for good beyond 100 N/mm² of admissible stress, whereas the 301 stainless steel of the MLS gaskets withstands 517 N/mm², 5 times more, and springs back at every combustion.
This page brings together the part numbers from two racing manufacturers, Athena and Cometic, in two constructions: Athena MLS with Gas Stopper and Cometic MLS multi-layer steel. Gasket bores run from 87.5 to 89 mm, covering the standard block as well as the rebored block, and thicknesses 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, one gasket per engine.
| Gasket bore OEM 88 mm | Thickness | Gasket volume | Gasket type OEM MLS | Brand | Part number OEM 12251-PCX-004 |
| 87.5 mm | 0.69 mm | 4.15 | MLS | Cometic | C4625-027 |
| 87.5 mm | 0.76 mm | 4.57 | MLS | Cometic | C4625-030 |
| 87.5 mm | 1.02 mm | 6.13 | MLS | Cometic | C4625-040 |
| 87.5 mm | 1.14 mm | 6.86 | MLS | Cometic | C4625-045 |
| 87.5 mm | 1.30 mm | 7.82 | MLS | Cometic | C4625-051 |
| 87.5 mm | 1.52 mm | 9.14 | MLS | Cometic | C4625-060 |
| 87.5 mm | 1.78 mm | 10.70 | MLS | Cometic | C4625-070 |
| 87.5 mm | 2.03 mm | 12.21 | MLS | Cometic | C4625-080 |
| 88 mm | 0.76 mm | 4.62 | MLS | Cometic | C4626-030 |
| 88 mm | 1.02 mm | 6.20 | MLS | Cometic | C4626-040 |
| 88 mm | 2.34 mm | 14.23 | MLS | Cometic | C4626-092 |
| 88 mm | 3.05 mm | 18.55 | MLS | Cometic | C4626-120 |
| 88.5 mm | 0.76 mm | 4.68 | MLS | Cometic | C4627-030 |
| 89 mm | 0.69 mm | 4.29 | MLS | Cometic | C4335-027 |
| 89 mm | 0.76 mm | 4.73 | MLS | Cometic | C4335-030 |
| 89 mm | 0.85 mm | 5.29 | MLS | Athena | 338124R |
| 89 mm | 0.91 mm | 5.66 | MLS | Cometic | C4335-036 |
| 89 mm | 1.02 mm | 6.35 | MLS | Cometic | C4335-040 |
| 89 mm | 1.14 mm | 7.09 | MLS | Cometic | C4335-045 |
| 89 mm | 1.30 mm | 8.09 | MLS | Cometic | C4335-051 |
| 89 mm | 1.42 mm | 8.83 | MLS | Cometic | C4335-056 |
| 89 mm | 1.52 mm | 9.46 | MLS | Cometic | C4335-060 |
| 89 mm | 1.68 mm | 10.45 | MLS | Cometic | C4335-066 |
| 89 mm | 1.78 mm | 11.07 | MLS | Cometic | C4335-070 |
| 89 mm | 1.91 mm | 11.88 | MLS | Cometic | C4335-075 |
| 89 mm | 2.03 mm | 12.63 | MLS | Cometic | C4335-080 |
| 89 mm | 2.13 mm | 13.25 | MLS | Cometic | C4335-084 |
| 89 mm | 2.18 mm | 13.56 | MLS | Cometic | C4335-086 |
| 89 mm | 2.34 mm | 14.56 | MLS | Cometic | C4335-092 |
| 89 mm | 2.49 mm | 15.49 | MLS | Cometic | C4335-098 |
| 89 mm | 3.05 mm | 18.97 | MLS | Cometic | C4335-120 |
| 89 mm | 3.56 mm | 22.15 | MLS | Cometic | C4335-140 |
Gasket volume: the space the gasket leaves above each cylinder. It enlarges the combustion chamber, and the larger it is, the lower the compression ratio. Values compare with one another at identical gasket bore.
| Fasteners | Engines | Tightening torque |
| Original cylinder head bolts 90005-PCX-003 | F20C1, F20C2, F22C1 | M11 bolts: 29 Nm, then 90°, then 90° (a further 90° for new bolts); 8 mm bolt: 22 Nm |
| ARP cylinder head studs ARP-208-4702 | F20C1, F20C2, F22C1 | 43 Nm, then 86 Nm, then 129 Nm |
Before fitting, check the flatness of the cylinder head and of the block with a straight edge and have them skimmed if necessary. None of these gaskets requires sealant: Athena and Cometic both supply them already coated.
| Reinforced ARP cylinder head studs F20C F22C → |
 | Athena MLS Two to five layers of AISI 301 stainless steel, laser cut, stamped and riveted. Around each cylinder, a layer folded over on itself, the Gas Stopper, concentrates the clamping load on the combustion chamber, while beads seal the water and oil passages. The outer layers receive a two-coat finish: the first withstands high temperatures and fills small irregularities on the block and cylinder head, the second, silicone based, keeps the gasket from sticking on disassembly. This is Athena's all-steel choice, from a prepared naturally aspirated engine to moderate forced induction. |
 | Cometic MLS Several stamped and riveted stainless steel layers. The outer layers carry active beads around each cylinder and each fluid passage. Sealing is achieved with a moderate clamping load and limited bore distortion. This is the versatile choice, from a prepared naturally aspirated engine to light forced induction. |
Gasket bore. The Athena MLS comes in 89 mm, the Cometic MLS in 87.5, 88, 88.5 and 89 mm.
Thickness. Honda does not publish the thickness of the original gasket. 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 | The value closest to the thickness of the removed gasket |
| Skimmed cylinder head, make up the lost height | The thickness of the removed gasket + what was removed |
| Forced induction build, lower the ratio | A thickness above that of the removed gasket |
| Naturally aspirated build, raise the ratio | A thickness below that of the removed gasket |
With a thickness finer than that of the removed gasket, measure piston protrusion above the block with a dial gauge: it is what determines the remaining clearance between piston and cylinder head.
 | Athena S.p.A. is an Italian manufacturer of engine gaskets and components, with its head office and main plant in Alonte, in the Veneto region. The group also produces in Spain, the United States, Brazil and India. Its multi-layer gaskets are fitted as original equipment by car manufacturers, and its racing range is designed and made entirely in Italy. |
 | Cometic Gasket, Inc. is an American manufacturer of engine gaskets and sealing solutions, founded in 1989 and based in Concord, Ohio. Its speciality is the made-to-order gasket, in the bore and thickness required. All its products are made in the United States, from American materials. |
| Criterion | Original gasket 12251-PCX-004 | Reinforced gaskets |
| Construction | Multi-layer steel (MLS) | Multi-layer stainless steel |
| Gasket bore | 88 mm | 87.5 to 89 mm |
| Thicknesses available | Not published by Honda | 0.69 to 3.56 mm, 19 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 |
| Honda S2000 (AP) | F20C1 | 231 and 243 hp | 1999-2003 |
| Honda S2000 (AP) | F22C1 | 239 and 243 hp | 2003- |
OEM part number: 12251-PCX-004.
Important: the F20B, F22A and F22B of the Accord and Prelude take other cylinder head gaskets: they are not covered by this page.
A reinforced gasket holds where the standard one reaches its limit: at higher combustion pressure it keeps its shape instead of being crushed.
As soon as power goes up, turbo, supercharger or raised compression ratio, the head gasket becomes the weak link of the top end. Switching to a reinforced gasket is then not a comfort but a safeguard: it is what prevents the failure and the head removal that comes with it.
