Cometic MLS 77mm Head Gasket for Honda Civic/CRX D15 & D16

Cometic MLS 77mm Bore Head Gasket for Honda Civic / CRX SOHC D15 and D16

Bore out a D-series to fit bigger pistons and the factory head gasket stops fitting. A stock D15 or D16 runs a 75mm bore. Go to 76mm or 76.5mm, and the edge of a stock-bore gasket hangs into the cylinder. That puts the gasket right in the flame on every combustion stroke, and it'll burn through. An overbored engine needs a gasket with a bore that's bigger than the new cylinders. That's what this Cometic gasket is for: a 77mm bore that clears overbored D15 and D16 blocks.

It's also an MLS gasket, made from stainless steel layers instead of a composite sheet. If you're overboring for more displacement, you're likely adding compression, a cam, or boost too, and all of that raises cylinder pressure. MLS holds its seal where a composite gasket would start to fail. Building a stock-bore D16? Use a gasket sized for 75mm. This one's for blocks that have been bored out.

Sizing the Bore Right

The gasket's bore has to be bigger than your cylinders, by enough that the gasket edge stays out of the flame. It shouldn't be so much bigger that you lose sealing surface or quench area around the cylinder for no reason. A 77mm gasket fits blocks bored up to just under 77mm, like a 76mm or 76.5mm overbore. Measure your finished bore before you order. Don't go by the piston box. Your machine shop's final number is the one that matters.

Three Layers of Stainless

The two outer layers are stainless steel embossed with raised beads around each cylinder and passage. When you torque the head down, those beads compress like springs and keep pushing back against the head and block. That's how the seal stays tight as the aluminum grows and shrinks with heat. A Viton coating on the outer layers, a fluoroelastomer rubber rated to 482°F (250°C), fills in tiny surface flaws. The plain stainless center layer sets the thickness, .030in on this one. MLS gaskets clamp evenly across the whole surface, so the cylinders stay rounder once the head's torqued down. The gasket doesn't need to be re-torqued after the first heat cycle, either.

Install Notes

An MLS gasket needs flat, smooth surfaces to seal against. Since the block's been bored anyway, have the shop deck it and check the head for flatness while they're at it. Get both surfaces to Cometic's MLS finish spec. Clean everything down to bare metal, install the gasket dry, and torque the head in sequence to spec. Factor the .030in thickness into your compression ratio math along with your pistons. For a boosted build, use head studs instead of the factory bolts.

Fitment

• Honda Civic and CRX with SOHC D15 or D16 engines - confirm your exact engine code before ordering
• 77mm gasket bore: for blocks overbored to just under 77mm
• .030in compressed thickness