Cometic MLS Head Gasket for K20Z3 (86mm & 87mm, .030)

Cometic K20Z3 MLS Head Gaskets - Part #C4561-030 / #C4562-030

The K20Z3 in the 8th gen Civic Si will take a lot of abuse before it complains, but once boost or big compression enters the picture, the head gasket becomes the fuse. These are Cometic's K20Z3-specific MLS gaskets in the standard .030 thickness, in stock 86mm bore or 87mm for engines that have been over.

What It Is and Why It Works

The construction is Cometic's proven 3-layer MLS: two embossed stainless outer layers coated in Viton, a fluoroelastomer that stays sealed to 482F, over an uncoated stainless center shim. The embossments distribute clamp load evenly across the deck, which reduces bore distortion and keeps ring seal consistent, and the stainless layers rebound with every heat cycle instead of taking a set. It seals an aluminum head to an aluminum block without sealant, and no re-torque is required after installation. This is the gasket to pair with head studs when the stock one taps out, or any time the head comes off and you would rather not reuse a 15-year-old part.

Specs

Available Options

Fitment

Also the right gasket for a K24 block wearing the 06-11 Si RBC head, since the gasket follows the head's bolt pattern, not the block.

What to Know Before You Buy

These fit the RBC-head bolt pattern, which is what makes them K20Z3 parts; the PRB-head engines (K20A2, K20Z1 in the RSX Type-S and EP3 Type R) use Cometic's C4311 family instead. On a K20/K24 hybrid, pick the gasket by which head you are running, not the block. Stock K20Z3 bore is 86mm, so only step up to the 87mm gasket if the block has actually been bored; running an oversized fire ring on a stock bore gives up quench area for nothing. The .030 thickness is the standard rebuild spec for this engine.