Cometic 89mm K-Series MLS Head Gasket C4313 - Sleeved

Cometic 89mm K-Series MLS Head Gasket - Part #C4313-040

An 89mm K-series is a sleeved block, full stop, and a sleeved block needs a gasket whose fire ring lands on the sleeve and not the parent bore. Cometic's C4313-040 is the 89mm 3-layer MLS in .040 compressed, the thickness most big-bore K builds land on once the deck has been cut and the piston has been chosen.

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

89mm is sleeve territory on any K-series. This gasket is for a Darton or Golden Eagle sleeved block; it will not seal on a stock or overbored factory cylinder.

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.

Confirm the sleeve OD and the finished bore with your machinist before you order. The fire ring needs full support all the way around; a gasket that overhangs a sleeve edge by even a half millimeter will push out under boost.

Only one thickness is stocked here. If the compression math calls for something else at 89mm, ask us; Cometic makes the C4313 in other thicknesses to order.