Cometic Honda K20/K24 MLS Head Gasket – 87.5mm Bore, .051″ Thickness | Acura RSX, Civic Si & K-Series Engines

Important: K20 vs. K24 Cylinder Bore Compatibility

Although K20 and K24 engines share Honda’s K-series architecture, they do not all use the same cylinder bore.

The 87.5mm gasket bore is particularly relevant to compatible K24 engines and appropriately configured performance builds.

However, gasket bore alone does not establish compatibility. The cylinder head, block, oil passages, coolant passages, and specific gasket design must also match.

Important: Do not assume this gasket fits every K20 engine simply because it is marketed as a K20/K24 product. A K20 with an 86mm factory bore may require a different gasket depending on the engine configuration.

Verified Manufacturer Part Number

The exact 87.5mm bore and .051-inch thickness combination is sold as Cometic H2004SP1051S. Cometic also lists C14039-051 with those dimensions for specific K20A2, K20A3, K20Z1, and K24A1 applications. Confirm which part number is printed on your product packaging before publishing.

Year, Make, Model and Engine Fitment

For the Cometic C14039-051 application family, the manufacturer lists:

These are the manufacturer-listed model families, filtered to the relevant engine codes.

Important: This does not establish blanket fitment for all Honda K20 and K24 engines, including the 2006–2011 Civic Si K20Z3 or later K24Z-series engines.

FYI: How to Choose the Correct K-Series Head Gasket

The K20 and K24 engines share many architectural features, but their factory cylinder bores differ. A K20 generally uses an 86mm bore, while a K24 commonly uses an 87mm bore.

An 87.5mm gasket may be appropriate for certain K24 configurations or specially prepared engine builds. It is not automatically the ideal gasket for every factory-bore K20.

Before installation, verify the finished cylinder bore, cylinder head oil and coolant passages, deck surface finish, piston-to-head clearance, and head fastener specifications.

For a technical reference on MLS sealing requirements, consult Cometic’s Automotive Performance Gasket Catalog.

Frequently Asked Questions

Will this fit a 2004 Acura RSX Type-S?

The C14039-051 is listed for the K20A2 engine used in the 2004 RSX Type-S. Verify the actual product part number before ordering.

Does it fit a 2005 Honda Civic Si?

Yes, the K20A3 engine is among the C14039-051 applications.

Can I use it on a K24/K20 hybrid engine?

Potentially, but hybrid combinations require verification of coolant and oil passages, bore clearance, and the particular cylinder head and block pairing.

Does this gasket include head studs?

No. This listing is for one cylinder head gasket only.

Is it suitable for a turbocharged K-series build?

MLS gaskets are commonly used in forced-induction engines, but reliability depends on correct engine preparation, tuning, and cylinder head clamping. No universal horsepower or boost-pressure rating is established.

When did the K series become THE Honda swap build?

Check out our DIY guide here on the K series.

Upgrade Your Honda K-Series Engine with Cometic

The Cometic 87.5mm MLS Head Gasket provides a performance-oriented sealing solution with .051-inch compressed thickness and engineered multi-layer stainless steel construction.

Whether you’re rebuilding an Acura RSX or assembling a custom K-series performance engine, proper gasket selection is critical to long-term engine reliability.

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