A turbo collector in Sweden owns an engine GM says no longer exists: an unused 4.5-liter Duramax V8 from a program GM canceled in its 2009 bankruptcy. The baby Duramax engine prototype Sweden’s Henrik Bengtsson bought in a parts deal is a great story and a dead end for buyers. The new Duramax engine news that matters is what GM builds for 2027: a huge 8.3-liter V8 for heavy-duty trucks and the same 3.0-liter six for half-tons.
Quick answer: The baby Duramax was GM’s 4.5-liter LMK diesel V8, canceled in 2009. One unused prototype surfaced in Sweden, The Drive reported on April 9, 2025. GM’s real 2027 diesels are a new 8.3-liter Duramax V8 (555 hp, 1,230 lb-ft) for heavy-duty trucks and the 3.0-liter six (305 hp, 495 lb-ft) for half-tons.
Last updated: November 3, 2026
What was the baby Duramax engine prototype in Sweden?
It’s GM’s LMK, a 4.5-liter turbodiesel V8 built to fit anywhere a small-block gas V8 did. According to The Drive’s April 9, 2025 investigation by Caleb Jacobs, the project began in 2005 for GM’s half-tons, and The Drive’s June 17, 2026 podcast put its torque goal at 520 lb-ft.
The clever part was the hot-vee layout. GM put the turbo in the valley between the cylinder banks, so exhaust reached the turbine sooner and boost built faster. Diesel tuner Gale Banks, who saw it in 2006, told The Drive it ran a 29,000-psi common-rail system.
Bengtsson found his on Blocket, a Swedish classifieds site, in a bundle with a turbo he wanted. GM customer service told him all prototypes were scrapped and that it offers no support or parts for the LMK. So it’s a display piece: Jacobs said in June 2026 that a friend couldn’t find anyone to swap it into a square-body Chevy.
The new Duramax engine for 2027 is an 8.3-liter V8
GM revealed the Duramax 8.3L Turbo-Diesel V8 on September 24, 2026. It’s rated at 555 hp and 1,230 lb-ft. It replaces the 6.6-liter L5P, which made 470 hp and 975 lb-ft in the 2026 Silverado HD according to Carscoops.
The 2027 Silverado HD and Sierra HD pair it with a 10-speed automatic and tow up to 20,000 pounds conventional or 38,000 gooseneck. GM builds it at its DMAX plant in Brookville, Ohio. GM’s heavy-duty announcement says trucks reach dealers from late 2026, with prices to come.
| Heavy-duty diesel | Horsepower | Torque | Torque per liter |
|---|---|---|---|
| GM Duramax 8.3L V8 (2027) | 555 hp | 1,230 lb-ft | 148 lb-ft |
| Ford 6.7L Power Stroke (high output) | 500 hp | 1,200 lb-ft | 179 lb-ft |
| Ram 6.7L Cummins | 430 hp | 1,075 lb-ft | 160 lb-ft |
| GM Duramax 6.6L L5P (2026) | 470 hp | 975 lb-ft | 148 lb-ft |
Why go so big? Displacement makes torque without straining parts. The 8.3 makes the same torque per liter as the old 6.6, while Ford squeezes 179 from its 6.7. Less output per liter means less stress per cylinder, the durability case Jacobs made in The Drive. Ford still tows more: 40,000 pounds gooseneck.
Which new diesel engines in 2027 can you get in a half-ton?
Only one. The 3.0-liter LZ0 inline-six carries into the redesigned 2027 Silverado 1500 at 305 hp and 495 lb-ft, the same as 2026, per Chevrolet’s 2027 Silverado release. Ram and Ford have dropped theirs, The Drive noted in June.
New for 2027, it’s offered on the Work Truck, which starts at $41,395 with destination before the diesel option. GM estimates 27 mpg highway in two-wheel drive.
Check the tow rating before you order. Chevrolet’s 2027 chart lists 12,000 pounds for the diesel in a Crew Cab 4WD with the Max Trailering Package, while GM Authority reported 13,300 pounds for the 2026 diesel. If your trailer falls between those numbers, a leftover 2026 is the better truck.
Should you wait for the 8.3 or buy a 2026 HD now?
Wait if you tow a gooseneck over 36,000 pounds, GM’s old maximum per Carscoops. Otherwise a 2026 gets you a known engine: the L5P dates to 2017, while the 8.3 is a first-year design with no prices or owner track record.
GM hasn’t published 8.3 prices or fuel economy yet. Comparing brands? Our 6.7 Cummins guide and our 2027 Super Duty engine story cover the rivals. Shopping a gas half-ton? Read our Silverado engine problems guide and the GM 6.2L V8 recall explainer first.
Duramax questions buyers ask
Did GM ever make a 4.5 Duramax?
GM built 4.5-liter LMK Duramax V8 prototypes in the mid-2000s and showed one in a Suburban HD Z71 concept at SEMA. It canceled the engine before production during its 2009 bankruptcy, and later told the Swedish owner of one surviving unit that every prototype was scrapped.
Is the 6.6 Duramax being discontinued?
In heavy-duty pickups, yes. Order guides reported by GM Authority and autoevolution in September 2026 list the new 8.3-liter as the only diesel for the 2027 Silverado HD and Sierra HD. The 6.6-liter L5P, rated at 470 hp and 975 lb-ft, stays in 2026 models still on dealer lots.
What is the new Duramax engine for 2027?
It’s the Duramax 8.3L Turbo-Diesel V8, which GM calls its first heavy-duty diesel designed and built in-house. It’s rated at 555 hp and 1,230 lb-ft with a 10-speed automatic, and it reaches dealers in the 2027 Silverado HD and Sierra HD from late 2026.
The baby Duramax engine prototype Sweden’s Bengtsson owns was built to make 520 lb-ft in a half-ton. GM’s 2027 half-ton diesel makes 495, and its heavy-duty diesel makes 1,230. Those two numbers are the ones you can actually put on an order sheet.