We researched and compared the top LLY head gasket kits available for the 6.6L Duramax diesel engine. Our evaluation is based on manufacturer specifications, industry standards, and aggregated owner feedback from thousands of real-world installations. Each kit was assessed for material quality, sealing performance, ease of installation, and long-term durability. Here are our findings to help you choose the right kit for your rebuild.
| Photo | Product | Score | Buy |
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Mahle Original 55909VS Head Gasket Kit Best Overall Includes MLS head gaskets, valve stem seals, and all necessary gaskets for LLY Duramax |
9.2 | 🛒 Check Price |
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ACDelco 19210389 Professional Head Gasket Kit OEM Grade GM original equipment design, includes graphite composite head gaskets |
8.9 | 🛒 Check Price |
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Fel-Pro HS 26267 PT Head Gasket Set Best Value PermaTorqueMLS head gaskets with laser-welded armor |
8.5 | 🛒 Check Price |
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ATP Automotive 106-1035 Head Gasket Set Budget Pick Includes graphite head gaskets and complete gasket set for LLY Duramax |
7.8 | 🛒 Check Price |
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Victor Reinz 04-10100-10 Head Gasket Set Premium Alternative Multi-layer steel head gaskets with elastomeric coating |
8.1 | 🛒 Check Price |
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DNJ Engine Components HG3150 Head Gasket Kit Complete Kit Includes head gaskets, intake/exhaust gaskets, and valve cover gaskets |
7.3 | 🛒 Check Price |
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Reinz (MAHLE) C3205 Head Gasket Set Specialist Choice Multi-layer steel head gaskets with nitrile rubber coating |
8.4 | 🛒 Check Price |
1. Mahle Original 55909VS Head Gasket Kit: Best Overall
In our evaluation, the Mahle Original 55909VS stands out as the best overall LLY head gasket kit. Based on owner feedback and the spec sheets, the MLS head gaskets provide exceptional clamping force and thermal stability, critical for preventing blown gaskets in modified trucks. The kit includes every gasket needed for the cylinder head and associated components, saving time sourcing parts separately. Mahle’s reputation in diesel circles is strong, and this kit lives up to it.
However, one limitation is that it does not include head bolts or studs. For high-horsepower builds, we recommend pairing it with ARP studs. If you are on a strict budget or only need a basic replacement, this may be more than you need. Skip this if you prefer a kit with bolts included.
- Multi-layer steel (MLS) head gaskets for superior sealing under high boost and EGT
- Complete kit with intake/exhaust manifold gaskets, turbo gaskets, and more
- OEM quality materials meet or exceed GM specifications
Pros: Excellent fitment and sealing track record; All gaskets included for a full top-end rebuild
Cons: Does not include head bolts or studs
2. ACDelco 19210389 Professional Head Gasket Kit: OEM Grade
The ACDelco 19210389 is the go-to choice for those wanting a factory-grade rebuild. We compared its specifications to GM service manuals, and it matches exactly. Owner feedback indicates it seals reliably at stock power levels and is straightforward to install. The kit covers all the essential gaskets for a head gasket job, making it a convenient one-box solution.
That said, the graphite composite head gaskets are not ideal for heavily modified engines running high boost or nitrous. They can be prone to failure under extreme conditions. If you plan to significantly increase power, consider an MLS kit instead. This is best for stock or mildly tuned trucks.
- Direct OE replacement for LLY Duramax engines
- Graphite composite head gaskets with steel core for reliable sealing
- Includes valve cover, intake, and exhaust gaskets
Pros: Perfect fit and OEM quality assurance; Trusted by dealerships and professional mechanics
Cons: Graphite gaskets may not handle extreme boost as well as MLS
3. Fel-Pro HS 26267 PT Head Gasket Set: Best Value
Fel-Pro’s HS 26267 PT kit offers MLS head gaskets at a price point that undercuts many competitors. In our research, the PermaTorqueMLS gaskets have proven durable in street and mild performance applications. The kit is comprehensive, covering the head gaskets and most other gaskets needed for a top-end rebuild. Owner feedback highlights the convenience of no retorquing.
However, we found a few reports of fitment issues when used with aftermarket cylinder heads, particularly with dowel pin alignment. If you are using OEM heads, this should not be a problem. Skip this kit if you have ported or non-OEM heads; consider Mahle or ACDelco instead.
- Multi-layer steel (MLS) head gaskets with PermaTorque technology
- Includes all gaskets for cylinder head, timing cover, and oil pan
- No retorquing required after installation
Pros: Great value for an MLS kit at a competitive price; PermaTorque design simplifies installation
Cons: Some users report minor fitment issues with aftermarket heads
4. ATP Automotive 106-1035 Head Gasket Set: Budget Pick
The ATP 106-1035 is a budget option for those who need to get their LLY back on the road without breaking the bank. Based on owner feedback, it works adequately for stock engines with no modifications. The kit includes all necessary gaskets for a head gasket replacement, and installation is straightforward.
However, the graphite head gaskets are a significant drawback for any truck that sees towing, heavy loads, or performance upgrades. Multiple reports indicate early failure under high EGTs or boost. We recommend this only for low-mileage, stock trucks that are not pushed hard. If you plan to modify or drive aggressively, invest in an MLS kit.
- Affordable alternative for budget-conscious rebuilds
- Graphite composite head gaskets with steel core
- Covers exhaust, intake, and valve cover gaskets
Pros: Lowest price among major brands; Decent quality for stock applications
Cons: Graphite gaskets less durable than MLS, prone to failure under high heat
5. Victor Reinz 04-10100-10 Head Gasket Set: Premium Alternative
Victor Reinz is a well-respected name in gaskets, and the 04-10100-10 kit brings their MLS technology to the LLY Duramax. We evaluated the materials and found the elastomeric coating helps conform to minor surface irregularities, reducing the risk of leaks. Owner feedback is generally positive for stock and lightly modified trucks.
On the downside, the price is on the higher side for what you get, and some users noted that the kit lacks a few gaskets found in more complete sets, such as the turbo gasket. If you want a full set without extra purchases, look elsewhere. This is best for owners who prioritize gasket quality and have a moderate budget.
- MLS head gaskets with premium coating for improved sealing
- Includes valve stem seals and all essential gaskets
- German engineering standards for precise fit
Pros: High-quality MLS gaskets suitable for moderate upgrades; Good sealing even on slightly warped surfaces
Cons: Higher price than some competitors with similar features
6. DNJ Engine Components HG3150 Head Gasket Kit: Complete Kit
The DNJ HG3150 is a no-frills kit aimed at cost-conscious buyers. In our research, it is often used for quick repairs on trucks that are being sold or for low-priority vehicles. The kit contains the basic gaskets needed, but the quality is noticeably lower than OEM. Owner feedback includes complaints about premature gasket failure and leaks within months.
We do not recommend this kit for any truck that is daily driven, towed, or modified. The graphite head gaskets are simply not up to the task. Skip this if you want reliability; it is best only as a temporary fix or for a parts truck.
- Budget-friendly kit with graphite head gaskets
- Covers most gaskets for head removal and reinstallation
- Suitable for emergency or temporary repairs
Pros: Very low price point; Includes many gaskets in one box
Cons: Graphite gaskets are not durable for long-term use; Fitment can be inconsistent; some gaskets may need trimming
7. Reinz (MAHLE) C3205 Head Gasket Set: Specialist Choice
The Reinz C3205 is essentially a premium version of the Mahle kit, with a nitrile rubber coating on the MLS gaskets that enhances sealing. We found this to be a top choice for owners who push their trucks hard, whether for towing or performance. Owner feedback highlights its reliability in high-boost applications.
However, the cost is higher than many competitors, and some users report that the coating can be damaged if the head or block surface is not perfectly clean. If you are doing a backyard rebuild without proper decking, you might be better off with a standard MLS kit. This is for serious enthusiasts who want the best seal possible.
- MLS head gaskets with nitrile coating for superior sealing
- Includes all gaskets needed for head gasket replacement
- Designed for high-performance and heavy-duty applications
Pros: Excellent sealing under high pressure and temperature; Durable coating reduces micro-leaks
Cons: Higher price point; May require surface prep for perfect seal
Frequently Asked Questions
What is the difference between MLS and graphite head gaskets for LLY Duramax?
MLS (multi-layer steel) gaskets consist of several layers of steel with coatings that allow them to expand and contract with the engine. They are more durable under high heat and boost, making them ideal for modified or heavily used trucks. Graphite composite gaskets have a steel core with graphite facing; they seal well at stock levels but can fail under extreme conditions. For long-term reliability, especially if you plan to increase power, MLS is the better choice.
Do I need to use head studs with a new head gasket kit?
Head studs are recommended but not always required. For stock or mildly tuned engines, factory torque-to-yield bolts can be reused if they are within specification, but many mechanics replace them. For higher power levels, ARP head studs provide more consistent clamping force and reduce the risk of gasket failure. Most head gasket kits do not include bolts or studs, so factor that into your purchase.
Can I reuse my LLY head gasket kit if I only removed the head briefly?
No. Head gaskets are designed to be used once. Once compressed, they lose their ability to seal properly. Even if the engine has not been run, the gasket may have taken a set from initial installation. Always replace the head gaskets with new ones when reinstalling the cylinder head.
What other parts should I replace when doing a head gasket on an LLY?
While the head gasket kit covers the gaskets, it is wise to also replace the head bolts or studs, coolant, oil, and possibly the thermostat and water pump if they are old. Many owners also choose to have the cylinder heads checked for cracks and decked flat. The valve stem seals included in the kit should be installed with new valve guides if worn.
How do I know which head gasket kit is right for my LLY?
Consider your engine’s power level and usage. For stock trucks, ACDelco or Fel-Pro offer reliable sealing. For mild modifications, Mahle or Victor Reinz MLS kits are a good balance. For high-performance or heavy towing, Reinz or Mahle MLS with coatings are best. Budget options like ATP or DNJ are only suitable for temporary repairs or low-power applications.
Our Verdict
After thorough research and comparison, the Mahle Original 55909VS head gasket kit earns our top pick for its outstanding MLS gaskets, comprehensive coverage, and proven reliability in both stock and modified LLY Duramax engines. For those seeking OEM-grade quality at a slightly lower price, the ACDelco 19210389 is an excellent runner-up, particularly for stock trucks. Both kits represent the best value for long-term durability and peace of mind.
Last reviewed and spec-checked: June 2, 2025. We re-check our picks and listings periodically.
