Cometic C5489-051 LS MLS Head Gasket Pair – 4.100″ Bore, .051″ Thickness | GM 6.0L & 6.2L V8

Why Choose Cometic MLS Head Gaskets for Your LS Engine?

GM’s LS engine family is widely used in performance builds because of its compact architecture, aftermarket support, and adaptability to numerous vehicle platforms.

However, cylinder head sealing becomes particularly important when increasing combustion pressure through turbocharging, supercharging, nitrous oxide, or higher compression ratios.

The Cometic C5489-051 uses multiple stainless steel layers with embossed sealing features designed to maintain pressure around the combustion chambers.

Its MLS construction helps accommodate normal thermal expansion and contraction between the cylinder head and engine block.

When properly installed, the gasket can provide durable sealing in demanding engine environments. Plan your LS1 swap using our DIY guide.

Unlike conventional composite gasket designs, MLS gaskets require carefully prepared mating surfaces. Cylinder head warpage, incorrect deck finish, or inadequate clamping can compromise even a premium gasket.

FYI: Why a 4.100-Inch Bore Matters on LS Engines

The gasket’s combustion opening must be large enough to accommodate the engine’s finished cylinder bore without allowing the sealing edge to extend into the cylinder.

Common factory LS engine bore dimensions include:

A 4.100-inch gasket opening provides additional clearance beyond the nominal factory bore on these engines.

However, gasket bore alone does not establish fitment. The cylinder head design, gasket passage alignment, and engine-specific sealing requirements must also match.

FYI: Check LS Block Deck Warpage Before Installing MLS Gaskets

An MLS head gasket is only as reliable as the surfaces it seals.

Before installing the Cometic C5489-051, inspect the cylinder heads and block decks for distortion, corrosion, and surface damage.

Our How to Check an LS1 Block Deck for Warpage Before Installing the Heads explains how to measure deck flatness with a precision straightedge and feeler gauges.

The guide discusses reference limits of 0.004 inch over a six-inch section and 0.008 inch across the deck. These figures apply to the referenced LS1 inspection procedure; verify the specific requirements for your engine and Cometic MLS gasket.

How to Install Cometic C5489-051 MLS Head Gaskets

1. Remove both cylinder heads according to the applicable GM service manual.

2. Inspect the heads for cracks, warpage, and damaged sealing surfaces.

3. Check the engine block decks for flatness and the surface finish required by Cometic.

4. Measure the finished cylinder bores and verify gasket compatibility.

5. Clean both sealing surfaces without using aggressive abrasives that can damage the deck.

6. Position the gaskets correctly over the cylinder head alignment dowels.

7. Install the cylinder heads using appropriate head bolts or studs.

8. Follow the correct tightening sequence, torque values, and fastener instructions.

9. Reassemble the engine, refill fluids, and check for leaks.

Installation tip: Never assume the torque procedure for aftermarket head studs matches the original GM torque-to-yield head bolts.

Year, Make and Model Fitment

Cometic’s application catalog includes the following vehicle families. These ranges are manufacturer catalog coverage, not a guarantee that every engine and trim fits.

Additional catalog applications include select Buick, Chevrolet Express, GMC Savana, Isuzu, Pontiac, and Saab models.

For Pro Street Online’s vehicle-fitment database, filter these applications by the exact engine code, cylinder bore, and gasket configuration rather than assigning the entire model-year range indiscriminately.

Frequently Asked Questions

Does the Cometic C5489-051 fit an LS3 6.2L engine?

The 4.100-inch gasket bore is larger than the LS3’s nominal 4.065-inch cylinder bore, and Cometic includes LS3 applications in its gasket catalog. Verify the final engine configuration before installation.

Can I use this gasket on a 6.0L LQ4 or LQ9?

These are compatible engine families listed for the product, subject to verifying cylinder head and block compatibility. Their nominal factory bore is 4.000 inches.

Will this gasket work on a turbocharged LS engine?

MLS gaskets are commonly used in forced-induction builds, but boost capability cannot be established from gasket dimensions alone. Proper tuning, surface finish, head clamping, and combustion control are essential.

Does the C5489-051 include both head gaskets?

The standard manufacturer part number represents one gasket. This Pro Street Online product is advertised as a pair containing two individual C5489-051 gaskets. Confirm that the bundle is configured to ship two units.

Does the .051-inch gasket thickness affect compression ratio?

Yes. Gasket thickness affects combustion clearance volume and piston-to-head clearance. Compared with a .040-inch gasket of the same bore, a .051-inch gasket adds approximately 2.38cc of clearance volume per cylinder.

Is this an MLX head gasket?

No. Cometic identifies C5489-051 as a three-layer MLS gasket, not an MLX stopper-layer gasket.

Upgrade Your GM LS Engine with Cometic

The Cometic C5489-051 MLS Head Gasket Pair combines three-layer stainless steel construction, a 4.100-inch gasket bore, and .051-inch compressed thickness for compatible GM LS-based V8 engine applications.

Whether you’re assembling a street-driven LS2, rebuilding an LS3, or preparing a modified LS engine for higher cylinder pressures, choosing the correct gasket and following proper installation procedures are essential.

Shop LS performance engine parts and replacement components at Pro Street Online