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6.6L Duramax LB7 Rebuild Part 4

Upward Momentum

Aug 6, 2019
In the previous installment (March 2019) of our '02 Duramax LB7 build we left off halfway through assembling the engine. After swinging the freshly built short-block into the engine bay we quickly set to work installing the Fleece Performance Cheetah turbocharger, Freedom Racing Engines rebuilt heads, ARP head studs, Merchant Automotive heavy-duty chromoly push rods, and much more. We're now ready to finish off the build and fire the beauty up for the first time.
Before we could turn the key, however, there were quite a few areas that we needed to address. In our quest for performance and reliability, while remaining emissions compliant wherever necessary, we opted to upgrade nearly everything along the way. We replaced the exhaust manifolds, up-pipes, and down-pipe with high-flow units from PPE Diesel. Fuel is handled with 60-percent-over injectors from Dynomite Diesel Performance, along with replacement high-pressure fuel lines (we hit up Merchant-Automotive's catalog for the full set of soft fuel lines). A Mishimoto aluminum radiator and thermostat set will keep the engine cool, while a Bank's Technicooler intercooler manages charge air temperatures. We also raided RockAuto.com for every accessory that could be replaced (with AC Delco parts, of course). And finally, the masters at DuramaxTuner.com set us up with the tuning needed to keep the engine running smoothly while hitting our power goals.
The culmination of hundreds of hours of work came when we turned the key for the first time and the dash lit up. Buying the truck in pieces meant that we had no idea what, if anything, would work when the time came to power the truck back up. Then came the moment of truth. After a quick prime of the fuel system the Duramax roared to life. We'll wrap up the project in Part 5 after we get some break-in miles on the engine and finally hit the dyno.
Photo 2/42   |   When we left off previously we had bolted the engine between the frame rails and had assembled it to the point of having the valvetrain in place. We pick up from that point as we continue towards the first firing.


Photo 3/42   |   To handle the task of moving the spent exhaust gasses we turned to the Duramax experts at Pacific Performance Engineering. We began by installing a set of PPE's high-flow exhaust manifolds. These manifolds are cast from high-silicon molybdenum iron, have larger diameter ports for better flow, and include pre-drilled and tapped bosses for EGT sensors.
Photo 4/42   |   The up-pipes, which connect the exhaust manifolds to the turbocharger, are also from PPE. These pieces are made from 11-gauge stainless steel with a .120-inch wall thickness and 2-inch outer diameter. We opted to wrap ours in Heat Shield Armor from Heatshield Products to aid in keeping the heat where it belongs, in the exhaust.
Photo 5/42   |   Rounding out the exhaust is a stainless steel down-pipe from PPE, which routes spent exhaust gases from the turbocharger to the tailpipe. The factory down-pipe is a restrictive crushed-oval shape, while the new unit from PPE is smooth and round. We opted to wrap the down-pipe in Heat Shield Armor as well.
Photo 6/42   |   Installing the exhaust system with the engine in the chassis made the entire process exponentially more difficult. Working with a mirror proved to be the most beneficial to the process as it allowed us to see the backside of the turbo. Seen here is the down-pipe mating surface and gasket. It's worth noting that the IHI turbo on the LB7 is the only that uses bolts and studs to secure the down-pipe. Later Garrett turbo equipped engines use a V-band clamp.
Photo 7/42   |   If you look really close you can see the bolts that attach the up-pipes to the rear of the turbo. These bolts are 12mm 12-point and are incredibly difficult to reach. You'll want to stock up on wobble joints and flex-head ratchets to get this job done. Naturally we replaced these with fasteners from ARP.
Photo 8/42   |   The entire exhaust system from PPE is made in the United States and CARB approved for use in all 50 states. Included are all the necessary gaskets, which are constructed of 304 stainless steel. A ceramic coating option is also available for a more custom look.

Fueled Up

Photo 9/42   |   In our quest for more power and reliability we settled on fuel injectors from the pros at Dynomite Diesel. The injectors flow 60-percent more fuel than factory and are capable of supporting up to 800 rear-wheel horsepower. We carefully lowered each of the eight diesel squirters into their respective bores and secured them with their hold down clamp and bolt.
Photo 10/42   |   Since LB7 injectors are housed below the valve cover the next task was to install the injector wire harnesses. Each harness controls two injectors and gets secured to the rocker shaft assembly. Care should be taken not to over torque the nuts on the injector studs.
Photo 11/42   |   Next, the fuel return line gets attached to the injectors and head with five banjo bolts. Because of their age and propensity for stripped we replaced these with new bolts from Merchant Automotive. Once the return line is in place the lower half of the valve cover can be installed.
Photo 12/42   |   The LB7 engine also had the bad habit of corroding the high-pressure fuel lines. Corrosion on the inside can flake off and damage the injectors along with external contamination being possible because of their through-the-valve-cover design. It's recommended to replace these lines whenever injectors are replaced or serviced. Not wanting to push our luck we picked up a set of new fuel lines from Dynomite Diesel when we ordered the injectors.
Photo 13/42   |   Routing the high-pressure fuel lines may seem like a daunting task at first glance. Thankfully they only go one way so it's impossible to do wrong. Keen eyes will notice we also added a PPE race fuel valve to the mix, which replaces the pressure relief valve and helps to eliminate potential low fuel rail pressure codes that are caused when the factory valve opens too soon returning excessive amounts of fuel to the tank. This part is also CARB legal, in case you were wondering.
Photo 14/42   |   Early Duramax engines relied on suction from the high-pressure CP3 fuel pump to scavenge fuel from the tank. This is not only hard on the CP3 but as power levels rise a steady flow of clean fuel becomes even more important. To sustain positive fuel pressure we turned to AirDog and their high-performance 165 gallon-per-hour 4G lift pump.

Cool Off

Photo 15/42   |   The factory Duramax intercooler is a pretty stout unit in its own right thanks to its large cast aluminum end tanks (as opposed to the plastic used by much of the industry). Thankfully the pros at Gale Banks Engineering found a way to improve on the design. The Banks Techni-Cooler has a 25-percent larger core area and 34-percent more volume overall. The result is cooler exhaust gas temperatures and higher air density. This too is CARB compliant (are you starting to see a theme yet?)
Photo 16/42   |   014 Lb7 Duramax Engine Build Part Four
Photo 17/42   |   Continuing the quest for optimized cooling we decided to ditch the factory radiator in favor of an aluminum version from Mishimoto. Along with being slightly larger than stock, this new radiator has a 100-percent brazed aluminum core and features TIG welding on all other joints. It also carries a lifetime warranty.
Photo 18/42   |   In the truck the intercooler mounts to the core support first, and then the radiator attaches to the back side of the intercooler. Banks provides the new hardware that is necessary for the intercooler to attach, otherwise factory mounting should be reused. You'll also need to swap over the transmission cooler line fitting from the factory radiator to the Mishimoto unit.
Photo 19/42   |   Duramax engines utilize a staged two-thermostat design to the cooling system. We opted for Mishimoto's high-performance thermostat set, which include thermostats that open at 185 degrees and 191 degrees, respectively.
Photo 20/42   |   The Duramax thermostat housing is a cast aluminum piece shaped much like an upside-down Y that connects the cooling passages of the two heads. With it in place we could move on to installing the front accessory drive.


Photo 21/42   |   The accessory drive is split into two parts, each attaching to their respective head with four bolts. The passenger side accessory bracket, seen here, locates the alternator, vacuum pump (if equipped), PCV valve, and a pair of idler pulleys. We once again tapped RockAuto.com to procure a new AC Delco tensioner and pulley set.
Photo 22/42   |   The passenger side bracket orients itself just in front of the fuel injection control module (FICM) and next to the oil fill tube. A pair of studs are used to attach the cold start valve, and the PCV breather attaches along the side.
Photo 23/42   |   Moving to the driver side bracket we find the power steering pump, which also provides power to the hydroboost brake booster, the mounting point for the A/C pump, and the location of the optional second alternator. Since we didn't know the history of really anything we replaced both the steering and A/C pumps with new AC Delco units from RockAuto.com
Photo 24/42   |   022 Lb7 Duramax Engine Build Part Four
Photo 25/42   |   Not knowing the history of our engine and finding the engine-side wire harness strewn in a box, we took the time to strip all of the old sheathing from it to inspect the wires and replace the worn covering. Once we verified everything was intact we covered the wires with high-quality heat-resistant loom.
Photo 26/42   |   While dirty coolant systems are typically not associated with Duramax engines we weren't taking any chances. During our build Sinister Diesel launched a coolant filtration kit for '01-'10 Duramax engines so we jumped on it. The kit routes a small amount of coolant through a CAT filter before returning it into the system.
Photo 27/42   |   Clean and dry fuel is one of the most important things to a modern diesel engine. Pulling from the Sinister Diesel catalog again we opted to install the company's CAT fuel filter adapter. The aluminum adapter allowed us to install a 2-micron CAT filter in place of the factory filter, which filters to about 7 microns.
Photo 28/42   |   We didn't want to just have a good running engine, we also wanted it to look the part as well. In addition to stripping and painting most of the engine's metal bits, we also upgraded hoses to blue silicone and added heat shielding where appropriate.


Over the course of 210,000 miles and nearly two decades of hard use much of the underhood rubber hoses had seen better days. We turned to the Merchant Automotive catalog and picked up OEM replacements for nearly every rubber hose in the fuel system.

Photo 33/42   |   While we were replacing hoses we also tapped Summit Racing to pick up a stainless-steel fuel line replacement kit from Dorman. This kit replaces both the feed and the return lines from the tank to the engine. Also included in the kit are new mounting brackets.
Photo 34/42   |   The factory hard lines are one-piece units, making removal difficult. To aid in installation, the Dorman kit comes in pieces with sections of flexible stainless-steel hose. We had good luck installing the return line, however the feed line was a different story as it kinked quite bad at one of the flexible junctions.

Tuned Up

Photo 35/42   |   Tuning is one of the biggest keys to a good running engine. Not knowing what tuning, if any, our donor engine had we turned to the pros at DuramaxTuner.com to both return our factory ECM to stock and write the tuning files for our application. Using the company's King SPADE tuner we were able to upload the EFILive file with ease.
Photo 36/42   |   The King SPADE came loaded with five different tunes of varying power levels, which are able to be shifted on-the-fly. Enabling this function is a five-position DSP-5 switch. The switch is a simple two wire installation, with both routing to specific pins on the ECM harness.
Photo 37/42   |   036 Lb7 Duramax Engine Build Part Four

Lube Up & Cool Down

Photo 38/42   |   Because so much of the engine was new we made the decision to go with a quality break-in oil for the first-fire and subsequent break-in period. For this we turned to Driven Racing Oil and their DBR 15W-40 diesel break-in oil. DBR aids in piston ring sealing while also protecting main bearings, camshafts, lifters, cylinder bores, and turbocharger bearings. This oil is also low in detergent and high in anti-wear additives such as zinc, phosphorus, and sulfur. Fun fact: Driven Racing Oil was initially developed for the team at Joe Gibbs Racing to help protect their high-performance NASCAR engines.
Photo 39/42   |   Before firing the engine for the first time we took the time to prime some of the more important components, including our Fleece Cheetah turbocharger. To do this we pulled the oil feed line off the top of the turbo and pumped oil directly into the bearing cartridge.
Photo 40/42   |   While the turbo oil feed line was disconnected we used the same pump to push oil back through the hose and into the blocks oil galleys. Doing this ensured that while the system wasn't fully primed there was at least some oil in all the important places before we attempted to crank the engine over for the first time.
Photo 41/42   |   To fill the cooling system, we tapped AMSOIL and the company's Heavy-Duty Antifreeze. Designed for over-the-road truckers and off-highway equipment this fluid is designed to last for 12,000 hours or 600,000 miles. In our Duramax application that would equate to an entire lifetime, maybe two.
Photo 42/42   |   041 Lb7 Duramax Engine Build Part Four


Jefferson City, MO
Superior, WI
Ventura, CA
Banks Power
Azusa, CA
Duramax Tuner
Dynomite Diesel Products
Heatshield Products
Wilmington, DE
Optima Batteries
Milwaukee, WI
Pacific Performance Engineering
Montclair, CA
Madison, WI
Sinister Diesel
Summit Racing