LLY Vs. LBZ – A Comparison of Two Best

While some newbies may want a vehicle for some exterior (body design) factors, critical automotive enthusiasts look beyond what the eyes can see. No wonder most analyses are centered on performance and efficiency, alongside other factors like physical structure.

LLY Vs. LBZ engines are frequent in the mouth of GM fans who argue for or against one or more engine brands in the Duramax lineup.

Although General Motors and Isuzu’s joint venture – DMAX manufactures the LBZ and LLY, it is essential to “crack the nut” and find out the difference between these diesel engines.

LLY Engine

lly engine
Image: DieselExperts

The LLY Duramax is a turbocharged 6.6 liters diesel engine from the Duramax lineup. It was released in the middle of 2004 as a product of GM’s initial attempt to strategically carry out an implementation of emissions demands on their line of diesel-powered trucks.

The engine was built with a 32-valve design having a direct injection high-pressure fuel rail and sophisticated aluminum cylinder heads. Due to the challenges of GM’s LB7 injectors, the LLY valve covers were changed to allow easy access to its injector without removing the covers of the valve.

The LLY debuted in mid-2004, and DMAX continued its production until 2005. Some of the vehicles from GM’s lineup that was fitted with the LLY include GMC Sierra, Chevrolet Silverado, and Hummer H1.

Read Also: LS1 vs. LS6 Engine: What’re the Differences

LBZ Engine

LBZ Engine
Image: DieselExperts

The LBZ is another diesel engine from GM’s Duramax lineup manufactured by DMAX. This engine was built to overcome the challenges of the LLY. It was designed with two VIN number-code – “2” and “D” respectively.

The VIN “2” was released around 2005 to early 2006. This particular LBZ utilized the LLY engine tuning since the “D” tuning experienced some delay before it could gain an EPA certification in order to be fully produced.

Meanwhile, the code “D” was released in 2006. DMAX continued its production until 2007. It was designed with a superior engine computer system tune which offered the capacity to produce extra torque and power output than its 2005 LLY counterpart.

The LBZ was fitted in the following vehicles from GM’s lineup; GMC Sierra HD, Chevrolet Silverado, Chevrolet TopKick, and Chevrolet Kodiak.

Read Also: LS3 vs. LS7 Engine: What’re the Differences?

LLY Vs. LBZ Engine Differences

Although the LLY and LBZ are both products of General Motors and Isuzu’s DMAX, the two engines are not of the same capacity.

The LBZ is a superior Duramax engine with improved power output, torque level, and maximum engine speed. The table below summarizes the difference between LLY and LBZ.

Years Code Power Torque Max Engine Speed
2004–2005 LLY GMC TopKick (LRX option),

Hummer H1, and Chevrolet Kodiak (LRX option)

310 bhp

at 3000 rpm

(800 Nm) 590 lb/ft at 1600 rpm Redline: 3,200 rpm


2006–2007 LBZ GMC TopKick (LPD), (Chevrolet Kodiak (LPD option) 310 bhp

at 3000 rpm

(820 Nm) 605 lb/ft at 1600 rpm Redline: 3,200 rpm
2006–2007 LLY (GMC Savana and Chevrolet Express) 250 bhp

at 3200 rpm

(624 Nm) 460 lb/ft at 1600 rpm Redline: 3,450 rpm

LLY Vs LBZ Injectors

The LLY Duramax 2004.5 – 2005 engines were fitted with straight-bodied injectors. The injectors were different from those on the newer LLY (2006) as well as the LBZ. The LBZ and LLY newer versions were fitted with tapered-bodied injectors.

However, even though the injectors seem to be similar, there were some slight differences. For instance, you could swap the LLY body in an LBZ cylinder head with a bigger O-ring.

Conversely, the injector on the LBZ will not align with the LLY cylinder head. The LLY Vs. LBZ injectors are obviously not exactly as many people believe.


Another obvious difference between these Duramax engines is the LLY Vs. LBZ VIN number. You can easily spot the difference in VIN code around the 8th digit of the VIN number on both Duramax engines. While the LLY has the code “2” at the 8th position of the VIN number, the LBZ has “D” at the same 8th position of its VIN number.

The Vehicle Identification Number (VIN) is located on a small sticker attached to the pillar of the driver’s door. You can also find it on the dashboard in front of the vehicle’s steering wheel at the driver’s side. Once you find the VIN, simply trace the 8th digit to identify whether you have an LBZ or LLY Duramax.

LLY Vs. LBZ Turbo

The LLY was built with a 63.38mm eleven-blade billet compressor wheel inducer and an exducer of about 88.22mm, and an extended tapered exducer of 91.78mm. This turbo was way larger than the LBZ eleven-blade 60.98mm billet compressor wheel inducer and 88.25mm exducer base.

LLY Vs. LBZ specs

The LLY specifications include the following details:

  • Block: Cast gray iron
  • Head: Cast aluminum
  • Injection: Bosch
  • Compression: 17.5:1
  • Power: 310 bhp (231 kW) at 3,000 rpm
  • Torque: 590 lb⋅ft (800 N⋅m) at 1,600 rpm

Comparably, the LBZ specifications are as follows:

  • Block: Cast gray iron
  • Head: Cast aluminum
  • Injection: Bosch
  • Compression: 16.8:1
  • Power: 360 hp (268.45 kW) at 3,200 rpm
  • Torque: 650 lb-ft (881 N.m) at 1,600 rpm.

LLY Vs. LBZ reliability

The 2006 – 2007 LBZ is more reliable than the 2004.5 – 2006 LLY. As a matter of fact, they were manufactured to curb the challenges that were associated with the LLY Duramax engines. 

Meanwhile, if you were contemplating LLY Vs. LBZ reliability, horsepower, and torque output improvement are other major reasons why the LBZ Duramax engine is a better option than its LLY counterpart.


Which is better LBZ or LLY?

The LBZ and LLY are both amazing engines from DMAX (GM and Isuzu joint venture). They have a similar operation, especially the transmission. Although they use similar Duramax parts, the LBZ differs slightly due to its superior 360 hp as against LLY’s 310 hp.

GM made the LBZ superior by adding more webbing in its main bearing regions, improved injector and fuel rails, larger turbo inlet, etc.

So, technically, the LBZ is better than the LLY engine. If you’re concerned about your engine’s horsepower and torque levels, the LBZ is most likely the suitable engine for you. This is why the GMC Sierra and Chevy Silverado are more in demand.

Are LLY and LBZ the same?

Basically, the 2006 – 2007 LLY and LBZ are similar. They were manufactured with the same valvetrain, displacement, layout/cylinders, cylinder head materials, compression ratio, etc. They both delivered similar horsepower output and torque levels.

Therefore, if you drive a Chevy with the 2006/2007 LLY engine, it is possible to use the same Duramax parts on an LBZ on your engine. 

Can I put an LBZ in my LLY?

You may not be able to get a satisfactory result when you put an LBZ in your LLY. For instance, the LBZ injector may not work with the LLY computerized system. In any case, if you choose to put an LBZ in your LLY, it will not go well as a direct drop-in. It will require a couple of swaps.

A successful replacement will require swapping out the Engine Control Module (ECM) in the LBZ. However, this is not an easy DIY operation; hence, you may have to consult an expert auto mechanic to do the job perfectly.

What year is LLY an LBZ?

The LLY engine was later replaced with an LBZ in 2006 when the manufacturer spotted some limitations in the former that needed improvements. The 2006 LBZ was indeed a superior version of the LLY counterpart.

Meanwhile, the LBZ was built with superior horsepower and torque output of 360 hp and 650 lb-ft, respectively. Conversely, the LLY was designed with a relatively lesser horsepower level of 310 hp and 520 lb-ft/605 lb-ft torque output levels for 2005/2006 LLY, respectively.

Is the LLY a good engine?

Of course, the LLY is a good engine. The engine is not only powerful but reliable. DMax worked on the LLY to ensure that the emission challenges with other diesel engines like L5P do not resurface in the LLY.

Also, the LLY was designed without a trace of the injector failure problems of LB7 engines. However, the LLY is mostly faced with overheating challenges. Nonetheless, the engine is relatively better than some diesel engines in the automotive industry.

How much HP can a stock LLY handle?

A stock LLY can handle up to 500 rear wheel horsepower (rwhp) output. Meanwhile, the engine is built to deliver around 310 flywheel horsepower output at 3,000 rpm. However, most Duramax engines’ horsepower can accommodate a boost up to about 600 hp.

In any case, the base horsepower level of the LLY engine is relatively superior to some other diesel engines. Nevertheless, if you desire a horsepower boost, it is possible with the LLY. All you need is to contact a GM-specialized auto technician.

Can a 2006 Duramax be an LLY?

Sure, a 2006 Duramax can be an LLY. Although the LLY was released in 2004, it continued till 2006. However, the 2006 Duramax LBZ was also released as a replacement for the LLY. This is because the LLY engine had a couple of issues when Chevy introduced it in mid-2004.

One of the major challenges of the LLY was overheating, among other discouraging issues. Both the LLY and LBZ were built with several mechanical similarities.

However, the 2006 LLY Vs. LBZ engines manufactured within the same year do not offer the same performance and reliability levels. Of course, the LBZ ranks better than its LLY counterpart due to the presence of minimal mechanical issues.

What year did LBZ start?

The LBZ engines started in 2006. The Duramax LBZ needed to come into the automotive market due to the shortcomings of its LLY counterpart. The LBZ was built with amazing features that clearly distinguished it from the LLY and other engines in the Duramax lineup.

The 2006 LBZ was a direct-injection diesel engine with a high-pressure fuel rail. It had a compression ratio of 16.8:1, 360 hp / 268kw @ 3200 rpm, and 650 lb-ft / 899 Nm @ 1600 rpm torque level.

The LBZ became so special for being the first diesel engine in the Duramax lineup to be paired with the 6-speed Allison 1000 series automatic transmission system.

What is the difference between 2005 LLY and 2006 LLY?

The main difference between the 05 LLY Vs. LBZ (2006 model) engines are basically tuning in the torque output level, which impacts the performance of the latter. The 2005 LLY had a torque level of 520 lb-ft at 1,600 rpm.

Conversely, the 2006 LLY was built with a torque level of 605 lb-ft at 1,600 rpm. Besides this, the 2005 LLY and the 2006 LLY had a lot of similarities, including 310 horsepower output, 3,250 rpm max engine speed, 835 lbs engine weight, etc.

How do you tell if a 2006 Duramax is an LLY or LBZ?

Identifying whether a 2006 Duramax is an LLY or LBZ is pretty easy. Firstly, inspect the 8th digit on the Vehicle Identification Number. The LLY has the code “2” on this position, while the LBZ has the code “D” on the same 8th position.

Secondly, the LLY is designed with red badges, while the LBZ is designed with blue badges. These are simple things you can identify with the eyes. It may not necessarily require any technical analysis to distinguish between the 2006 LLY and LBZ.

Final Words

Irrespective of the fact that the LLY and the LBZ are from a similar lineage, it is obvious that both Duramax engines differ in various regards.

So, if you’re analyzing LLY Vs. LBZ, ensure to take cognizance of the improved torque and horsepower output of the LBZ, among other factors.

Meanwhile, from the review above, the LBZ is undoubtedly more reliable than all the LLY years in every aspect. Therefore, if you’re contemplating which of the GM Duramax engine is best, you have had the answer already.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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