Ever wanted to do an LB7 vs LBZ comparison? Well, your dream has just come true! Ok, corny jokes aside, in this post I will be doing a comparison between these two engines to establish which one is better than the other and in what ways. The LB7 and LBZ are, respectively, the 1 st and 3 rd generations of the Duramax engine.
During the mid-90s, GM was basically being torched by Ford and Dodge in the mid-size diesel truck market. These 2 companies had engines that far surpassed anything that GM and Chevy had. In response, GM partnered with Isuzu to produce the first Duramax which was the LB7.
It has since gone through several remakes to date. Which is the better option between the LB7 and the LBZ though? For many people, the LBZ is the best pre-emissions Duramax engine ever made by GM.
The LB7 was the first generation Duramax and a great engine that is popular with the hot rod community because it can be tuned to produce as much as 1000HP.
In short, the core difference between Duramax LB7 and LBZ is the fact that LB7 has 300 hp and 560 lb-ft of torque with a fuel tank size of 26 Gallons whereas the LBZ has 360 horsepower and 650 lb-ft of torque with a fuel tank size of 34 Gallons.
What is the difference between LB7 and LBZ?
These two are both great engines with their own set of unique pros and cons. In order to get a better appreciation of these two engines, I will dig a little deeper into the history of the 2 engines.
When the LB7 hit the market, it was able to give great competition to what Ford and GM were offering at the time. It was a great engine that produced amazing power and to date, is a favorite among tuners who can get a lot of power out of this beast.
However, it came with a major weakness which was the fuel injectors. They tended to fail often and repairing or replacing them tended to be a huge drag.
The failure of these injectors was largely linked to poor design. Accessing the injectors to replace or repair them meant you had to remove many other unrelated parts in order to reach them. This made the task very laborious. The next generation between these two was the LLY.
This engine managed to solve issues with the injectors but has problems with the connecting rods which tended to break often especially when modifications were made. After this, the LBZ finally came onto the market.
This engine solved the Duramax problems in both its predecessors offering stronger control rods as well as a better fuel injection system that was a lot easier to access. Ultimately, this meant that it became the perfect engine, a reputation it holds to this day.
Its production run only ran 2 years which is strange considering that it was a great engine but around that time, the conversation on emission was starting to get louder so car companies began to develop cleaner engines.
If you want to purchase the LBZ today, you would need to be prepared to fork out a decent amount of money as the price has continued to go up even as demand rises.
Together with the LB7, the LBZ is also a tuner’s dream but it does have its limits. The only time that this engine begins to have problems is when it is tuned.
If it is tuned above 700HP, the pistons tend to break. Some maintain that this figure is actually around 500HP. Another common issue linked with tuning is the Alison transmission slipping.
Though it is not as common, another issue that has been reported is transmission line leak and water pump issues. These are not as common but can happen. The water pump issue is a big one though because of how difficult the pump is to access should it need to be changed.
The LB7 also has better gas mileage when compared to the LBZ.
Can you put an LBZ Duramax Engine in an LB7 truck?
Ever wondered if you can swap out one of these engines for the other? Is it possible? Yes, you can convert an LB7 to an LBZ engine as most of the components are compatible including the instrument cluster. This is possible in the 2003 to 2005 trucks.
Conclusion on lb7 vs lbz
So, there you have it. I’ve given you the major pros and cons of both engines. The choice is yours on which one to pick. They are both great engines with a lot of ability. Though they were last produced nearly 2 decades ago, they are still very popular among vehicle enthusiasts to this day.
The LB7 in particular is a Hot Rod enthusiast’s dream because of the sheer power you are able to get out of it. 1000HP tuned is by every measure a great achievement.
At the end of the day, the choice is yours on whether you want to go for reliability or power. If the former, the LBZ is the way to go. If you want a Hot Rod, then the LB7 is the way to go.
Thomas is a retired Chevy Auto Technician, Father to two incredible daughters. He enjoys using his knowledge and experience to help you solve and find reliable information on Chevrolet vehicles.