Twin-Turbo GMC Syclone Makes 1,738hp With A Stock L8T Crank

For years, Justin New simply guessed at how much power his GMC Syclone was making. That guessing game is over. A recent dyno pull put his twin-turbo GMC Syclone at 1,738.4 horsepower and 1,246.4 lb./ft. of torque, numbers that landed far beyond what New expected walking into the session.

New’s truck is not just any Syclone. It is serial number 1373 of only 2,800 ever built, and that rarity shaped nearly every decision on the build. He kept the truck’s fenders and hood uncut, working within the factory dimensions rather than chopping into a piece of GMC history. That constraint pushed him toward a twin-turbo layout using Pulsar Turbo Systems 79/75mm turbochargers rather than a single big turbo, since a twin setup left him enough room under the hood while preserving the all-wheel-drive system and transfer case that make a Syclone a Syclone.

Guessing Game Ends On The Dyno

Before the pull, New had been telling himself the truck was making somewhere between 1,400 and 1,500 horsepower, even though Holley kept telling him the number was higher. He said he did not want his own high expectations crushed by a bad pull, so he stayed conservative in his head. A Wallace Racing calculator, based on the truck’s weight and its eighth-mile speed, ended up landing within 70 horsepower of the actual dyno result, proof that the math was closer than his gut feeling. The pull was made on a Mainline DynoLog dynamometer, with the truck hitting its peak horsepower at 7,838 RPM and its peak torque at 7,015 RPM.

The engine backing up that number is a GM LS V8 that’s fitted with a stock GM L8T crank. The truck’s a 4L80 transmission and transfer case, built by New Performance Racing Transmissions, keep the twin-turbo GMC Syclone all-wheel-drive. A Tick Performance ultra-low-profile intercooler and piping built by Jeremy Brown handle charge cooling. Fuel comes from an Aeromotive Fuel Systems in-tank 7.0 brushless pump, and Eric Mullis handled the 12-bolt rear end, along with injectors and brakes. Circle D Specialties built the 252mm converter, and Nicolas Feliciano of Nicolas Auto Repair tuned the truck.

The engine has made a good number of passes at its current 34 pounds of boost, though New says he has pushed it to 39 pounds. Feliciano told him he did not fully trust the MLS head gaskets much past that point, not because failure was imminent, but because there was no real reason to chase a bigger dyno number to hit New’s goals. New said friends running similar Cometic MLX gaskets on better fuels have seen 40 to 45 pounds of boost survive, and if he ever pulls the engine for a refresh, he plans to have the heads O-ringed to Top Fuel-style specifications for more headroom.

Chasing A Syclone Record

The drivetrain build has not been without drama. New broke an input planetary gear in the 4L80 at Street Car Takeover in Nashville, and Suncoast stepped in with a billet planetary set to get the truck back on track.

New’s next goal is the Syclone world record. The truck has already matched the record’s mph and come within a tenth of a second of the elapsed time record. Since the truck is set up for no-prep racing, New has been working on dialing in his 60-foot times on prepped surfaces, with a best of 1.24 seconds to 60 feet and a top speed of 143 MPH in the eighth-mile. He has not yet landed both numbers in the same pass.

There is also a story behind the truck’s name. New calls it Smokey because it caught fire and burned three days after he bought it in 2024, forcing him into a full rebuild and rewire before the truck ever became the record-chasing machine it is today.