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Start ShoppingCOMETIC C9523 MLS Head Gasket - Durable Seal for Panhead/Shovelhead/Evo Big Twins
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Description
Upgrade your Harley-Davidson engine's sealing system with COMETIC's C9523 MLS head gasket. Engineered for Panhead, Shovelhead, and Evo Big Twin applications, this durable solution ensures peak performance and long-term reliability for powersports enthusiasts.
Key Features
- Multi-Layer Steel (MLS) Construction: Superior heat resistance and sealing integrity for high-performance engines
- 0.040 in (1.02 mm) Thickness: Optimal compression and durability for heavy-duty use
- 3.437 in (87.30 mm) Bore Size: Precision fit for original equipment specifications
- 4.125 in x 4.125 in Outer Dimensions: Perfectly sized for easy installation and secure sealing
- Head Gasket Design: Ensures proper combustion chamber sealing and coolant/ oil integrity
Why Choose This Product
Cometic's C9523 delivers unmatched reliability for classic and modern Big Twin engines. The MLS construction prevents warping and maintains sealing integrity under extreme temperatures. Its precise specifications ensure perfect fitment, while the durable design reduces maintenance needs and extends engine life. Ideal for riders demanding peak performance from their Harley-Davidson machines.
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Upgrade your Harley-Davidson engine's sealing system with COMETIC's C9523 MLS head gasket. Engineered for Panhead, Shovelhead, and Evo Big Twin applications, this durable solution ensures peak performance and long-term reliability for powersports enthusiasts.
Key Features
- Multi-Layer Steel (MLS) Construction: Superior heat resistance and sealing integrity for high-performance engines
- 0.040 in (1.02 mm) Thickness: Optimal compression and durability for heavy-duty use
- 3.437 in (87.30 mm) Bore Size: Precision fit for original equipment specifications
- 4.125 in x 4.125 in Outer Dimensions: Perfectly sized for easy installation and secure sealing
- Head Gasket Design: Ensures proper combustion chamber sealing and coolant/ oil integrity
Why Choose This Product
Cometic's C9523 delivers unmatched reliability for classic and modern Big Twin engines. The MLS construction prevents warping and maintains sealing integrity under extreme temperatures. Its precise specifications ensure perfect fitment, while the durable design reduces maintenance needs and extends engine life. Ideal for riders demanding peak performance from their Harley-Davidson machines.
| SKU | GM37DAC6D1 |
|---|---|
| MPN | C9523 |
| Brand | Cometic |
| Category | Gaskets/Seals |
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Featured Review
| Make | Model | Years |
|---|---|---|
| Harley-Davidson | Panhead Big Twin | 1948-1984 |
| Harley-Davidson | Shovelhead Big Twin | 1966-1984 |
| Harley-Davidson | Evolution Big Twin | 1984-1999 |
Frequently Asked Questions
Designed for 3.437 in (87.30 mm) stock bore on Panhead, Shovelhead, and Evo Big Twins.
Multi-layer steel (MLS) for superior sealing under high compression.
No, 0.040 in thickness is standard replacement height for stock setups.
No, this is stock bore only. See Cometic for oversized options like C9523-055 for 3.552 in bore.
Installation Guide
Difficulty
Medium
Est. Time
1 hr 0 min
Tools Required
- torque wrench
- gasket scraper
- socket set
- head bolt kit
Pro Tips
- Clean deck surfaces to bare metal
- Use assembly lube on bolts
- Torque in 3 stages following Harley pattern
Common Mistakes to Avoid
- Not cleaning surfaces thoroughly
- Incorrect torque sequence
- Reusing old head bolts
Comparison vs Stock/OEM
MLS construction vs. OEM composite; better for high compression and performance builds
Improvements
- Superior sealing
- Handles higher cylinder pressures
- Resists blowout
Considerations
- Requires flat, clean surfaces unlike softer OEM gaskets
Durability & Warranty
Expected Lifespan
Engine rebuild lifespan (50,000+ miles with proper torque)
Warranty
1 year Cometic manufacturer warranty
Maintenance
Inspect during top end service; re-torque head bolts after 500 miles
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