The 6.6L Duramax LBZ was launched in 2006 as the successor to the LLY engine variation. However, the LBZ had a short-lived lifespan, only lasting until 2007 when it was replaced with the LMM which due to new emissions regulations. The LMM was designed to be more eco-friendly for stricter emissions laws which ultimately resulted in the discontinuation of the LBZ.
When it comes to power, the LBZ was given a significant boost over its predecessor, increasing horsepower and torque to 360hp and 650tq. The power increase made it a strong competitor against the Cummins and ill-fated Powerstroke engines of the time. Additionally, the performance and tuning capabilities of this engine created a huge market for it amongst diesel performance guys.
Along with the stout performance, the engine was available with the Allison 1000 automatic transmission, one of the absolute best and favorite transmissions across diesel and commercial vehicles. For those opting for a manual, the 2007 LBZ was the last Duramax that could be paired with a manual transmission, the ZF650 six-speed.
LBZ 6.6L Duramax Applications, 2006-2007:
- Chevy Silverado HD 2500/3500
- GMC Sierra HD 2500/3500
- Chevy Kodiak
- GMC TopKick
Duramax 6.6L LBZ Specs
| Engine Variation | 6.6L Duramx LBZ, V8 turbo diesel 90 degree |
| Production | 2006 – 2007 |
| VIN Code | D (8th digit) |
| Engine Size | 6.6L, 403 cubic inches |
| Head Material | Aluminum |
| Block Material | Cast iron |
| Compression Ratio | 16.8 : 1 |
| Min. Cylinder Pressure | 300psi |
| Timing Order | 1-2-7-8-4-5-6-3 |
| Bore | 103mm, 4.055″ |
| Stroke | 99m, 3.897″ |
| Turbocharger | Garrett GT3788VA |
| Fueling & Injection | Direct injection; 26,000psi Bosch rail |
| Valvetrain | Overhead Valve OHV |
| Oil Capacity | 9.5L (~10 quarts) |
| Weight | 835 lbs. |
| Idle RPM’s | ~680 |
| Max RPM’s | 3,250 |
| Peak Horsepower | 360hp at 3,200 rpm’s |
| Peak Torque | 650lb-ft. at 1,600 rpm’s |
| Dimensions (LxWxH) | 30x30x32 inches |
Duramax LBZ Reliability
The LBZ is quite possibly the most desirable Duramax made to date. Reined as the last Duramax diesel before emissions standards significantly changed diesel engines, and touted for its strong straight-from-the-factory performance, the LBZ is by all means an awesome engine.
To prepare for the increased power, Duramax strengthened the block with more webbing, 4mm deeper bores, and stronger main bearing caps. The rods were changed to forged steel and the design was improved to handle more power. On this engine, the rods and block aren’t extremely capable and likely won’t give you any problems.
However, the pistons were still made out of cast aluminum which made them prone to cracking at high horsepower. Additionally, the Garrett turbocharger ran into vane stick problems occasionally resulting in need to remove the turbo.
Overall, the Duramax is an extremely reliable engine and is highly capable. Tuned and upgraded LBZ’s will be less reliable without upgraded pistons and rings, but very rarely do either of these cause issues on stuck LBZ’s. The LBZ’s are widely regarded as the best and most reliable Duramax made.
Read our 5 Most Common LBZ Duramax Engine Problems post here!
Duramax LBZ Common Engine Problems
- Pump Rub & Transfer Case Failure: the transfer case inlcudes a gear pump inside of it that is controlled via the mainshaft. Because of this, the housing for the pump floats in the rear housing. Over time, the pump rubs against the housing which can lead to a leak since the housing is very thing. This does not become noticeable until the whole transfer case is shot from lack of fluid.
- Pistons: while this is really on a problem for high-horsepower LBZ’s, the pistons are known to crack around 600rwhp and shouldn’t be pushed too far above that
- Allison Transmission Limitation: unless you fully build the Allison transmission, it gets capped out at around 450whp. So while this isn’t necessarily a problem, it’s a limitation for anyone looking to further upgrade their LBZ.
- Water Pump Failure: water pumps are known to go out every ~100k miles or so. The OEM water pump has a plastic impeller inside of it (the thing responsible for pushing the fluid) and over time through normal wear and tear, the plastic deteriorates until the impeller no longer functions. When the impeller goes back, the pump is no longer able to flow the coolant at high enough pressures, resulting in overheating.
6.6L LBZ Performance & Tuning Potential
In addition to coming out of the factory with more power than the 6.0L Powerstroke and the 5.9L Cummins, the 6.6L LBZ Duramax was one of the most tuneable as well.
While the pistons are a concerning issue on these engines, you shouldn’t run into any issues until you’re trying to push serious power. We recommend keeping it under 650rwhp and 1,050lb-ft. to prevent any issues of cracking pistons. If you are looking to break those barriers, we suggest upgrading to forged pistons and rings.
The stock turbo and injectors are capable of approx. 525rwhp. The biggest limitation for going beyond 450rwhp is going to be the Allison transmissions. Beyond those levels, you’ll likely need to drop around $5k to get your Allison fully built.
Here are some popular bolt-on mod options for the LBZ:
- Intake / Cold Air Intake
- EFILive Tune: 30-120hp depending on supporting mods and aggressiveness of tune (approx. $800)
- Downpipe / Exhaust: Boosted Performance LBZ Downpipe
- Intercooler Piping
- Transmission Flash
- Lift Pump
View our in-depth best Duramax LBZ mod guide.