Cometic 88mm K-Series MLS Head Gasket C4312 - .040 to .060

Cometic 88mm K-Series MLS Head Gasket - Part #C4312-040 / -045 / -051 / -060

Once a K24 goes to 88mm, or a K20 gets sleeves, the stock-bore gaskets are done. Cometic's C4312 is the 88mm 3-layer MLS, and it's sold here in four thicknesses from .040 to .060 because an 88mm build is almost always a compression-ratio conversation as well.

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

88mm is an overbore on every K-series. This gasket is for a K24 taken out a millimeter or a sleeved K20; it does not seal on a stock 86 or 87mm bore.

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.

The .060 is where you land when you're running a K24 block with a K20 head and want to pull static compression down for boost without changing pistons. The .040 is for a naturally aspirated 88 that only needs clearance after a deck cut. Everything in between is a piston-maker calculation.

Measure the bore and check the fire ring lands fully on the sleeve or cylinder wall. An 88mm gasket on an 87.5 sleeve leaves the ring hanging over the edge and it will blow out.