Cometic 89mm MLS Head Gasket for S2000 F20C/F22C

Cometic 89mm F20C/F22C MLS Head Gasket - Part #C4335-030 / C4625-051

The F20C and F22C leave the factory at 87mm, so an 89mm gasket is for a sleeved or overbored S2000 block and nothing else. That's a specific customer: a built F22C on sleeves, a boosted F20C that's been taken out for pistons. Cometic's 3-layer MLS in .030 or .051 is what seals that engine, and the thickness is how you land the compression ratio.

What It Is and Why It Works

Cometic's MLS gasket is three layers of stainless steel: two embossed outer layers coated in a Viton fluoroelastomer that seals against the block and head, and a center shim that sets the compressed thickness. The Viton handles 250 C, the stainless springs back after every heat cycle instead of taking a set, and the layered design tolerates the slight movement between an aluminum head and block that kills a composite gasket. It's the same construction Honda uses from the factory, done with more clamp margin.

Thickness is how you set compression and piston-to-valve clearance after a deck cut or a piston change. Thicker gasket, lower static compression, more clearance; thinner, the reverse. Cometic sells the same gasket in several thicknesses for that reason, and the bore has to clear your actual cylinder bore, not the one the engine left the factory with.

Specs

Fitment

The F20C and F22C are 87mm from the factory. This gasket is for a block bored or sleeved to 89mm; a stock-bore S2000 takes Cometic's 87mm F-series gasket.

What to Know Before You Buy

Surface finish matters more than anything else. Cometic wants the block and head decked to 50 RA or smoother; an MLS gasket on a rough or corroded deck will weep coolant no matter how it's torqued. Have the head checked for flatness and skimmed if it's been overheated.

Match the gasket bore to the finished bore, not the sleeve nominal. The fire ring has to land fully on the sleeve or cylinder wall.

The F-series head is a known warp risk after overheating. Have it checked flat before an MLS goes on; it will not compensate for a wavy head the way a thick composite might.