Honda K20C1/C4/C8 Engine Head Gasket 12251-RPyY-G02

Genuine Honda Head Gasket (12251-RPY-G02) - K20C1, K20C4 & K20C8

The head gasket is the one seal you cannot afford to get wrong, and on a boosted engine it's under considerably more pressure than a naturally aspirated build ever asks of it. This is the genuine Honda multi-layer steel gasket for the K20C, the same part these engines left the factory with. If you're putting a head back on, this is what goes between it and the block.

Why MLS Is The Right Technology Here

Multi-layer steel is what Honda uses on these engines, and on a turbocharged application it's the only sensible approach.

MLS gaskets work by having thin steel layers with embossed beads that spring against the deck and head surfaces. That spring maintains sealing pressure through thousands of heat cycles as everything expands and contracts, and it recovers rather than relaxing the way a crushed composite gasket does.

On a boosted engine, cylinder pressure is doing its best to lift the head off the block on every combustion event. A gasket that maintains its clamping load is what stops that becoming a problem.

Your Deck Surface Matters More Than The Gasket

Worth saying plainly, because this is where head gasket jobs actually fail.

MLS gaskets need a good surface finish to seal properly. They're less forgiving of a rough or damaged deck than a composite gasket, because they're sealing metal against metal rather than filling imperfections with a soft material.

So before this goes on, check your deck and head for flatness with a straightedge, and get them machined if they're out of spec. Clean both surfaces properly. And don't use sealant, MLS gaskets are designed to go on dry and adding sealant can prevent them seating correctly.

A perfect gasket on a warped head leaks. A perfect gasket on a properly prepared surface lasts the life of the engine.

Replace Your Head Bolts

Important, and it's advice that gets ignored regularly.

Honda's head bolts on these engines are torque-to-yield, meaning they're designed to stretch permanently during torquing. That stretch is what generates the clamping force.

A bolt that's already been stretched once has done that job. Reusing it means you're not getting the clamping load the design calls for, which is how a properly installed gasket ends up leaking anyway.

So plan on new head bolts, or go to a proper stud kit if the engine is being built for more than stock output. On a boosted K20C making real power, studs are worth serious consideration regardless.

An Honest Note On Big Power

Being straight, because it matters on these engines.

The factory MLS gasket is excellent for what Honda designed it around, which is stock or near-stock boost levels. It's the correct part for a rebuild, a repair, or a moderately tuned car.

If you're pushing serious boost, the head gasket becomes one of the first things that limits you, and that's why aftermarket MLS gaskets in various thicknesses exist alongside stud kits. For a stock rebuild or a sensibly tuned car, this is the right part. For a big power build, look at a dedicated performance gasket and proper studs.

Do It Once

Pulling a head is most of the labor on this job, so use the access.

Inspect your valve guides and seals while everything is exposed. Look at your timing components, since the front of the engine is likely apart anyway. And if cams or valve springs are anywhere in your plans, this is the moment rather than doing the job twice.

Fitment

2017-2021 Honda Civic Type R (FK8)
2023-2026 Honda Civic Type R (FL5)
2018-2022 Honda Accord 2.0T
2019-2025 Acura RDX
2021-2025 Acura TLX
2024-2026 Acura Integra Type S

Covers the K20C1, K20C4, and K20C8. Part number 12251-RPY-G02.

Who Should Grab One

This is for anyone putting a K20C head back on, whether that's a rebuild, a repair after a gasket let go, or a head refresh on a high mileage engine. It's the genuine Honda part at a price that makes reaching for a copy hard to justify, given that the labor to install it dwarfs what the gasket costs. Prep your surfaces properly, use new bolts, and torque it to spec.

Fits: Honda K20C1, K20C4, and K20C8, see the application list above. Part number: 12251-RPY-G02. Type: genuine Honda multi-layer steel head gasket. Installation: install dry on a properly prepared surface, no sealant. Recommended: new head bolts or a stud kit, since factory head bolts are torque-to-yield.