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6.6L Duramax

Diesel of the Week

1,900-Plus HP LLY Duramax Engine

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After trial and error and a lot of lessons along the way, Morey Logue made it his goal to hit 2,000 horsepower with his 6.6L LLY Duramax engine, a feat that only a few have conquered. He hasn’t made it quite yet, but he’s about as close as he could be.

Logue moved out to Layton, Utah, just outside of Salt Lake City, two years ago, and began working at Interstate Diesel Performance as a technician. It’s a one-stop shop that does everything from oil changes to performance overhauls. However, his current stint at Interstate isn’t where his project began.

“Way back in like 2010, a buddy of mine had a 12-valve Cummins, and I think my interest started around then as it did for a lot of people when they found out you could pull the fuel plate out of it to give it some more horsepower,” Logue says. “That was pretty cool, and we did a lot of tinkering on it. A year later, I bought my first Duramax.”

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Over the next couple years, Logue bought and worked on a Cummins before focusing on other things. However, he was drawn back into the diesel world rather quickly.

“A buddy of mine had the Duramax I have now sitting in his barn for maybe two years or so,” he says. “I knew the thing was supposed to be pretty fast, so we discussed it for a while, then I finally made the deal.”

Logue started working on a race build straight away, and the initial goal was to make it into the Diesel Power Challenge. In 2020, he was in the running for the event, with his first setup making around 1,000 horsepower on fuel and 1,100 on nitrous.

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Covid put a halt on the event permanently, but at the time, it was probably in the best interest for Logue to pass up competing anyway. He had guessed that the engine was on its last leg, and sure enough, a tear down shortly after confirmed his suspicions. Since then, he’s dropped another Duramax under the hood and started a journey to improve the performance of his LML as much as possible.

“It’s been a learning curve for sure,” he says. “We went through a lot of pushrod failures and had to switch brands, had some issues with the alternate firing cam and getting that to breathe right, and on one run it blew the V-band clip off the atmosphere charger and that caused a ton of issues.”

Trial and tribulation often bring the best results though, and Logue’s current setup boasts an incredible 1,925 horsepower. Just short of his ultimate goal, the truck is rocking some intense upgrades. The 6.6L Duramax is an LML block with LLY electronics in the truck.

The engine features Manton pushrods, Wagler valve springs, Wagler ported and polished heads, Ross forged pistons, and a Callies Ultra billet crank. Also from Wagler are the billet main caps and their Duramax street girdle. The girdle and everything else on the engine uses ARP hardware.

The turbo system changed a few times over the course of the build, with Logue eventually settling on a High-Tech turbo 83/87 in the valley and a Garrett GT5541R on the atmosphere. All of the fabrication work for the setup was done in-house by Interstate Diesel.

“The turbos work great and spool perfectly,” Logue says. “I discussed what more we could do with some people, and we decided that a second CP3 would work well, so now there are two injection pumps from Industrial Injection – a 12mm and a 10mm.”

A FASS 290 lift pump provides the engine with enough fuel and protects the injection system. Logue runs four solenoids from Nitrous Express and Turbo Smart wastegates, all with 35-lb. spring zones. A Mishimoto intercooler rounds out the engine build.

“I want to get that 2,000 hp at least once,” Logue says. “Maybe if I had held my tongue just right in the cab, I would’ve hit it already. But it’s coming. After that, I’ll probably downsize it a bit and get back down to around 1,300 horsepower for racing.”

Expect to see Logue and the team at UCC in a few weeks, where he’ll be putting his build to the ultimate test!

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Diesel of the Week is sponsored by AMSOIL. If you have an engine you’d like to highlight in this series, please email Engine Builder Editor Greg Jones at [email protected]

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