lly vs lbz

LLY vs LBZ Duramax (Similarities and Differences Explained)

The Duramax engine has been a staple in the GMC and Chevy lineup for years. It’s a powerful and reliable engine that has become a favorite among truck enthusiasts. There are two versions of the Duramax engine, the LBZ and the LLY. Both engines are great, but there are some key differences that truck enthusiasts take into account when choosing which one is right for them.

LBZ vs LLY Main Differences

When it comes to comparing the LBZ and LLY Duramax engines, the main difference between the two comes down to power and torque. The LBZ engine is more powerful, with 360 horsepower and 650 lb-ft of torque at 1600rpm. On the other hand, the LLY engine has 310 horsepower and 605 lb-ft of torque at 1,600rpm. So, if you’re looking for more power and performance, the LBZ engine is the way to go.

The LBZ Duramax has an engine capacity of 6.6 liters, providing enough power to propel heavy-duty pickups such as the GMC Sierra ,the Silverado by Chevrolet. GM also added more features such as:

  • Webbing in the main bearing parts
  • Taller caps in the main bearing
  • Deeper bores(4mm) for the cap bolts*

With simplicity, more power and reliability, GMC hit the jackpot. However, LBZ was short-lived, and it had to be phased out in 2007 due to the new emission regulations. The LMM was introduced thereafter.

Specifications of the LLY Engine

  • Block / Head: 5″4Cast gray iron / Cast aluminum
  • Bosch high-pressure common-rail
  • 3000 rpm and 310 bhp in power and torque
  • 17.5:1 compression ratio

Specifications of the LBZ Engine

  • 6.6 liters engine capacity
  • 16.8:1 compression ratio
  • V8 diesel ,’turbo
  • Aluminum head and cast-iron block
  • 360hp and 650tq

LLY and LBZ Similarities

The LLY has major similarities to the LBZ that remain to be seen. Both engines have a similar displacement of 6.6 liters that acts as a housing to 32 valves.

The two engines also have a V8 engine layout running on diesel. The layout is based on two bank cylinders sharing a V-shaped crankshaft.

Later versions of the LLY engine were still in production at almost the same time (2006-2007) as the earlier versions of the LBZ.

Why the LBZ is Unique

LBZ’s biggest flex was being the ultimate last engine that was unlimited by the emission restriction technology. The technology reduced engine lifetime and performance on models that were later manufactured.

As the first Duramax engine with the Allison 1000 six-speed automatic transmission, the LBZ had the capability of handling more. The Duramax LBZ was packed with strong and durable parts that had an immense result on performance and lifespan.

The LBZ had more substantive steel forged rods, which enabled it to handle an excess of 100 horsepower as compared to its predecessors. The CP3 fuel pump by Bosch was crucial in generating extra pressure to compliment the new and reinforced injectors and rails.

With a larger inlet turbo pipe, bottlenecks previously hampering the charger from maximum efficiency were minimized. Trucks with the LBZ engine are still going strong in demand for more than 15 years since inception.

FAQ Section

How many horsepowers Can a Stock LLY Handle?

Straight out of the factory, a stock LLY can handle about 500 to 600hp without tuning.

Is The LBZ The Same as the 2006 LLY?

In the year 2006, GM debuted the LLY VIN 2 (code “2”). The (code “2”) LLY was mechanically identical to the LBZ and was equipped with the six-speed transmission from Allison. However, it retained the LLY designation due to longer certification timeframes by the EPA that delayed production.

How Can You Identify an LLY from an LBZ?

The LBZ engine has blue badges (Allison Duramax) while its counterpart the LLY has red badges (Duramax diesel). The LBZ also has “D” as the 8th number on the VIN serial while LLYs have a “2” as the 8th number.

Is The LLY a Good Duramax Engine?

Yes. The LLY Duramax has been known to be powerful, reliable, and unlike modern diesel engines, it has minimal emissions. Trucks with the LLY Duramax engine have minimal injector problems that were previously witnessed in the LB7 vehicle engines.

Apart from the L5P, the LLY can also be tuned to match the power of all the other Duramax engines.

What Year of Duramax is Best?

Of all the six Duramax engines, past to present, the 2006-2007 LBZ model is astoundingly the best. The LBZ is a step up from its predecessors, which have head gasket and injector issues. Its design gives the engine massive tune-up potential.

The lack of emission control technology means that the engine is more superior and reliable as compared to the other five models.


With some models being more popular than others, each of the Duramax engines has its shortcomings and strong points. Modern engines offer more torque, horsepower and tune-up capability, while pre-2007 models offer more reliability and superiority.

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