The Best Upgrades for Duramax LBZ Diesel Engines

The Duramax LBZ is, in many ways, the crown of all Duramax diesel engines. It was the last one produced before efficiency regulations required regeneration and diesel particulate filters, yet it was also produced after Duramax switched to the Bosch common rail injector system that supported higher pressures. Even this mechanical masterpiece can be improved with a few upgrades, however. If you drive a GMC 6.6L V8, here are the best LBZ Duramax upgrades.

More Capable Allison Transmission

If you make many LBZ Duramax upgrades, you’re going to have to also upgrade the Allison transmission.

The stock transmission that this engine came paired with was a six-speed Allison 1000 that could handle about 400 rwhp. The engine is capable of up to about 600t to 650 rwhp, though, and just a few upgrades can take you there. Once you exceed 400 rwhp, talk with a knowledgeable diesel mechanic about rebuilding or replacing the original transmission. A customized Allison 1000 is perfectly fine, but it’ll have to be professionally adjusted.

Larger Diameter Downpipe

When you pull the transmission, you should also use the opportunity to change out the downpipe. Replace the stock setup with one that’s 3 inches in diameter, and you’ll have better airflow leaving the engine. This is a fairly inexpensive replacement once the transmission is taken out.

Larger Diameter Exhaust

Further improve airflow through the system with a bigger exhaust. A 4-inch piece will quickly usher exhaust gases away, and it’ll be especially helpful if you install a turbocharger  (see last upgrade).

Aftermarket Lift Pump

The Duramax LBZ didn’t come with a lift pump, instead using a suction valve to pull fuel up and into the engine. Although this setup is sufficient for everyday driving, high-performance demands a more reliable fuel supply. An aftermarket lift pump will provide the stable fuel supply that high-performance driving needs.

Variable Geometry Turbocharger

Bolt a variable geometry turbo directly to the Duramax LBZ for high-flow performance. The turbo will increase the air going through your engine, and that means there’s more oxygen to burn. Step on the accelerator, and you’ll instantly feel the difference after one of these is installed.

Over-Injecting Fuel Injectors

To burn that extra oxygen, the engine needs more fuel delivered to it. Pair that variable geometry turbo with over-injecting fuel injectors, so you can take full advantage of all the available air. Together, these two upgrades can reach the maximum power output of the Duramax LBZ engine.