How It's Made: The Duramax Diesel Engine

1012Dp How Its Made Duramax Diesel Assmbled Engines

Ten years ago, nobody knew what a 6.6L Duramax engine was. We couldn't tell how they worked, how long they would last, or the power output they'd be capable of making. Ten years, and more than 1.3 million engines later-we know the answers to all those questions.

As a Diesel Power reader, you've seen hundreds of stories in our pages discussing the Duramax. We've tested it, talked about its design, and showed you how to modify it. The one piece of the story you've been missing, however, has been how these engines are built.

Where The Magic Happens Duramax engines are manufactured in Moraine, Ohio, by DMAX Ltd. This is a joint venture between General Motors and Isuzu. When originally conceived, DMAX Ltd. was 60 percent owned by Isuzu and 40 percent owned by GM. Today, that ratio has swapped, and GM is the majority owner.

There are a number of things that make the DMAX facility different from other GM engine plants. The most significant is that it hot-tests 100 percent of the engines it produces. That means every 6.6L engine is run on a dyno before it ever goes in a truck. No other GM engine mass produced in North America gets that treatment-nor do the 6.7L Cummins or 6.7L Power Stroke engines.

In The Plant We spent an entire day in the DMAX plant with our cameras and got to ask all the questions you'd ever want answers to. The facility is huge and well laid out. The raw materials enter the west end of the building and progress easterly as the blocks, heads, rods, and cranks are machined. The facility is well lit, safety oriented, and filled with workers who care about what they're building. The only two things we weren't allowed to photograph were the machines used to adjust each engine's valvetrain, and the dyno cells.

Watching the system that sets the Duramax valve lash is like watching a Terminator robot perform open heart surgery on another Terminator. Each engine's rotating assembly is spun multiple times, and a series of what look to be laser-range finders and electronically driven sockets adjust the valve lash.

The dyno cell is even more impressive. Each engine is placed on a stand that slides into its own dyno room. The engines are fed preheated oil and coolant to bring them up to operating temperature. The dyno spins the engine over to start it-there's no need to use the starter motor. Each engine is run on diesel to ensure its full-rated power output. We don't know if we'll ever be able to stop smiling after witnessing dozens of Duramax engines making dyno pulls!

DMAX LTD: By The Numbers Location: Moraine, Ohio Plant size: 584,000 square feet Employees: 415 hourly, 117 salaried Union: IUE-CWA Local 755 Year facility opened: 1999 Beginning of production: July 17, 2000 Production capacity: 200,000 engines a year Number of engines built on day of our visit: 320 Total number of Duramax engines built: More than 1.3 million

Thank You, DMAX! Our special thanks go out to Tom Read of GM Powertrain, and Maho Mitsuya, Steve James, and Courtney Strickler of DMAX Ltd. for making our visit possible. We also want to thank the men and women of the IUE-CWA Local 755 union for letting us come into their workplace and allowing us to share their success story with our readers. Keep up the great work!

Morale at the DMAX plant is high. There's a pride and honor that you can see and feel in the facility, as well as in its people.
Morale at the DMAX plant is high. There's a pride and honor that you can see and feel in t
The Duramax gray-iron engine blocks are cast at GM's Defiance plant in Ohio. They arrive at DMAX Ltd. looking like this. Note the lack of head boltholes.
The Duramax gray-iron engine blocks are cast at GM's Defiance plant in Ohio. They arrive a
The blocks are loaded onto a transfer line where they undergo multiple machining operations. This robotic arm scoops the blocks up and routes them to machines that bore, thread, and mill all the critical surfaces.
The blocks are loaded onto a transfer line where they undergo multiple machining operation

Each block experiences a multistage boring process to ensure the cylinders are round and square to the deck surfaces.
Each block experiences a multistage boring process to ensure the cylinders are round and s
The top 2 inches of the cylinders are induction-hardened to radically reduce cylinder-wall wear caused by the piston rings. These leopard-spot-like markings, caused by the hardening process, are not visible on new blocks, as the final honing process erases them.
The top 2 inches of the cylinders are induction-hardened to radically reduce cylinder-wall
The forged-steel crankshafts begin life at a Sumitomo plant in Japan. They arrive at the DMAX plant in this raw state and are machined, balanced, and nitrided (case hardened) onsite.
The forged-steel crankshafts begin life at a Sumitomo plant in Japan. They arrive at the D

Finished cranks are transferred to the assembly line, where the timing gears are pressed onto their snouts.
Finished cranks are transferred to the assembly line, where the timing gears are pressed o
The forged-steel connecting rods also come from Japan, and they're machined at the DMAX plant. The connecting-rod caps are cracked off to form a rock-solid fit when bolted back together around the crank. You can see a video of the process at www.dieselpowermag.com.
The forged-steel connecting rods also come from Japan, and they're machined at the DMAX pl
The finished rods are fitted with bolts, hung on racks, and moved to the assembly line.

Isuzu casts the aluminum heads in Japan, and they arrive in Ohio in this unfinished form.
They are CNC-machined for the valves, head bolts, and injector hold-downs.
The assembly process begins with freshly machined blocks being loaded onto the line. The blocks make a righthand turn, are cleaned, dried, and flipped upside down.
The assembly process begins with freshly machined blocks being loaded onto the line. The b

The crankshafts are coded, and this scanner logs which crank is fitted with which engine block.
The crankshafts are coded, and this scanner logs which crank is fitted with which engine b
The cranks are then lowered into the block. An assembly worker installs the main-bearing caps that sit in a tray hanging from the side of the engine's skirt.
The cranks are then lowered into the block. An assembly worker installs the main-bearing c
The timing gears are bolted onto the roller camshafts, and the assembly is slid into the block.
The timing gears are bolted onto the roller camshafts, and the assembly is slid into the b

Each rod is mated with a piston and wristpin by a machine.
A conveyor belt carries the rod and piston combos to the main assembly line, where workers use a pneumatic piston installer to insert them into each engine.
A conveyor belt carries the rod and piston combos to the main assembly line, where workers
The '11 LML Duramax uses a higher-output oil pump than previous engines. The new pump is installed by hand and secured with air tools that hang from the ceiling.
The '11 LML Duramax uses a higher-output oil pump than previous engines. The new pump is i

At this stage, the aluminum front and rear timing covers are bolted on, and the oil pan is sealed. The oil cooler is also installed before the water pump goes on.
At this stage, the aluminum front and rear timing covers are bolted on, and the oil pan is
New for '11, is this Bosch CP4 injection pump that must be precisely timed with the cam and crankshaft position. A special hoist is used to lift each pump into place, and a digital photo is taken of the engine's timing marks to guarantee proper alignment. Then, this second tool is used to fasten the pump to the engine.
New for '11, is this Bosch CP4 injection pump that must be precisely timed with the cam an
A robot pressure-tests the coolant, oil, and piston ring seals before the head gaskets and cylinder heads are installed on the engine. A second robot then torques the 18 head bolts (per head) at the same time.
A robot pressure-tests the coolant, oil, and piston ring seals before the head gaskets and

Then the exhaust manifolds, intake manifolds, pushrods, and rocker shafts are assembled before the valve covers are bolted down.
Then the exhaust manifolds, intake manifolds, pushrods, and rocker shafts are assembled be
Each Bosch piezo injector is slid into place by hand, and the hold-down clamps are secured.
Each Bosch piezo injector is slid into place by hand, and the hold-down clamps are secured
A robotic scanner is used to document each injector's flow rate and location in order to create a unique engine calibration for each engine.
A robotic scanner is used to document each injector's flow rate and location in order to c

Every engine is hand-fitted with dozens of small fasteners, fuel lines, and brackets to complete the long-block assembly. As each engine moves down the line, there is a three-level parts tray that follows it.
Every engine is hand-fitted with dozens of small fasteners, fuel lines, and brackets to co
A Garrett turbo is hoisted into place and bolted down before the EGR cooler and plumbing is installed.
A Garrett turbo is hoisted into place and bolted down before the EGR cooler and plumbing i
The completed engines are set on these test stands. A drive hub is bolted to the flexplate in order to couple the engine to a dyno. Every single Duramax engine is hot-tested on a dyno for eight minutes.
The completed engines are set on these test stands. A drive hub is bolted to the flexplate