Cometic C5245-040 Chevrolet Gen I Small Block V8 MLS Cylinder Head Gasket

Chevrolet Small Block Engine Compatibility

The Cometic C5245-040 belongs to Cometic’s Gen I Chevrolet small-block gasket family, covering compatible engine configurations using 18-degree and 23-degree cylinder heads.

Potential engine families include:

• Chevrolet 283 small-block V8
• Chevrolet 305 small-block V8
• Chevrolet 307 small-block V8
• Chevrolet 327 small-block V8
• Chevrolet 350 small-block V8
• Chevrolet 383 stroker V8

Important: These are engine-family references, not a guarantee that the 4.060-inch gasket opening is ideal for every factory bore. The actual cylinder bore, head design, and gasket passage alignment must be verified.

A 400 small-block Chevrolet requires particular attention to its larger factory bore and steam-hole requirements. The 4.060-inch C5245-040 should not be used on a stock-bore 400.

FYI: Why a 4.060-Inch Head Gasket Bore Matters

A head gasket’s combustion opening must be correctly sized for the engine’s finished cylinder bore.

For example, the Chevrolet 350 small-block typically has a factory bore of 4.000 inches.

A common .030-inch overbore increases the cylinder diameter to 4.030 inches, making gasket selection particularly important during engine assembly.

The Cometic C5245-040 provides a 4.060-inch gasket opening, which can accommodate properly configured 350 engines with a 4.030-inch finished bore.

However, gasket bore is only one factor. The cylinder head’s combustion chamber shape, coolant passages, and engine block deck condition must also be compatible.

Why Choose Cometic MLS for a Small Block Chevy?

Traditional small-block Chevrolet engines remain popular because of their simple architecture, extensive aftermarket support, and proven performance potential.

However, cylinder head sealing becomes increasingly important when engine builders introduce higher compression ratios, aftermarket aluminum heads, aggressive camshafts, or forced induction.

The Cometic C5245-040 uses multiple stainless steel layers with embossed sealing surfaces designed to maintain clamping pressure around the combustion chambers.

Its MLS construction helps accommodate normal thermal expansion between dissimilar engine materials.

When installed on properly prepared mating surfaces, this design provides a durable sealing solution for compatible performance applications.

Installation Recommendations

1. Verify the engine’s finished cylinder bore.
2. Confirm cylinder head compatibility and coolant passage alignment.
3. Inspect the cylinder head and engine block deck for warpage and surface damage.
4. Check that the mating surfaces meet Cometic’s MLS surface-finish requirements.
5. Clean both surfaces without scratching or gouging them.
6. Install the gasket according to the manufacturer’s instructions.
7. Use appropriate head bolts or studs and the specified tightening procedure.
8. Check piston-to-head clearance and compression-related dimensions during assembly.
9. Reassemble the engine and verify cooling system operation.
10. Inspect for coolant, oil, and combustion leaks after startup.

Installation Tip: MLS gaskets require careful surface preparation. Do not apply additional gasket sealant unless specifically directed by the manufacturer.

Frequently Asked Questions

Does the Cometic C5245-040 fit a Chevy 350?

Yes, it is intended for compatible Gen I small-block Chevrolet configurations, including properly matched 350 engines using appropriate 18-degree or 23-degree heads.

Will this gasket fit a 383 stroker?

It may fit a 383 built from a compatible 350-style block, provided the finished cylinder bore and head configuration match the gasket.

Can I use it on a 400 small-block Chevy?

Not on a factory-bore 400. The stock 400 cylinder bore is 4.125 inches, larger than this gasket’s 4.060-inch opening.

Does this gasket fit an LS1 or LS3 engine?

No. GM LS engines use a different block and cylinder head architecture and require LS-specific head gaskets.

Does this include two head gaskets?

No. Cometic C5245-040 is sold individually. A complete V8 head gasket replacement generally requires two gaskets.

Is this gasket suitable for turbocharged or supercharged applications?

It can be considered for properly engineered performance engines. Reliable sealing depends on combustion pressure, engine preparation, cylinder head clamping, and tuning.

Upgrade Your Small Block Chevy with Cometic

The Cometic C5245-040 MLS Head Gasket combines a 4.060-inch bore, .040-inch compressed thickness, and three-layer stainless steel construction for compatible Chevrolet Gen I small-block V8 engines.

Whether you’re restoring a classic Chevrolet or building a performance-oriented small-block, selecting the correct head gasket is essential for dependable engine operation.

Shop Chevrolet engine components and performance replacement parts at Pro Street Online.