Installing Edelbrock’s 6.6L Duramax Cylinder Heads

Normally, when issues like damage and high mileage make replacing the cylinder heads on a 6.6L Duramax diesel engine necessary, most people use rebuilt stock heads. This has been the standard practice because replacement aftermarket heads—especially aluminum—simply aren't available in massive quantities.

Enthusiasts in search of more power are in a similar situation, relying on reconditioned factory heads that are sometimes ported and upgraded with aftermarket valvetrain hardware. Edelbrock, a company well known for producing performance cylinder heads for gas-powered engines, has changed that in a big way.

With the release of the 6.6L Duramax cylinder head, Edelbrock becomes one of only a few aftermarket companies to offer performance-oriented cylinder heads for diesel engines. This direct-bolt-on aluminum head is a great alternative for replacing worn-out heads and increasing performance and durability.

Designed to be ready to run out of the box, the Edelbrock heads are compatible with all stock Duramax valvetrain components, along with valve covers, the water crossover, injectors, and glow plugs. The heads are made from A356 aluminum castings that are heat- and pressure-treated to reduce porosity in order to increase the strength and fatigue properties of the material. Created to be more than just replacement heads, the intake and exhaust runners are engineered to optimize the flow and swirl of incoming and exiting air. Further enhancing the heads is extra material in the deck for increased strength and in the ports to allow for custom porting.

Something that makes these heads particularly appealing to many is the fact that they are CARB legal, meaning they can simply be bolted on as replacements for those old, damaged, or high-mileage stock units without any emissions worries.

Hearing a well-known company like Edelbrock has developed a new cylinder head for diesel engines definitely piqued our interest. So, as soon as we could get our hands on a set of the Duramax heads, we got in touch with our friends at FTK Diesel in Boardman, Ohio, to map out a plan to install them and evaluate their effect on a late-model Duramax engine.

Ray McClelland Jr., the proprietor of FTK Diesel, owns the '14 GMC Sierra 3500HD daily driver/tow rig we selected for this project. It was chosen because the engine has never been taken apart, and the modifications it has are fairly common for 6.6L Duramax LML engines. The updates include a Tater Built Turbo Chargers & Machining modified stock turbocharger, a 12mm CP3 injection pump, a Fuelab Velocity 100-gph lift pump (with FTK Diesel install kit), and a street tune. Backing the engine is a stock transmission with custom tuning to help it hold up to more than 500 hp.

To get a true feeling for what the new Edelbrock diesel cylinder heads can do, we decided to also upgrade the stock intake and exhaust manifolds, as well as the up-pipes during the installation. A Wehrli Custom Fabrication '11-to-'16 Duramax LML High Flow Intake Bundle Kit and a PPE Ceramic-Coated High-Flow Exhaust Manifolds and Up-Pipes Kit were enlisted to allow the engine to breathe.

The first order of business before FTK Diesel's Technician David Schiel turns a wrench is to put the truck on the dyno to get a performance baseline. For projects like this, having before and after dyno numbers gives us data that qualifies exactly what the heads are capable of doing.

Before removing the turbocharger, the downpipe and up-pipes have to come off. The same turbo will be going back in, but the pipes are being replaced with better flowing PPE and Wehrli Custom Fabrication tubing.

The injectors, fuel rail, and corresponding lines are removed from the heads, as are the valve covers, rocker shaft, and pushrods. David then unbolts and lifts the heads of the engine.

Merchant Automotive sent us a Duramax Head Gasket Kit (LML) that includes all the gaskets, seals, glow plugs, head studs (ARP), and miscellaneous items needed to do the top end of a Duramax engine. It also shipped a Heavy-Duty Pushrod Kit.

With the block cleaned and inspected, David begins the reassembly process. After the head is set in position, the ARP head studs are installed and tightened by hand.

New Merchant Automotive heavy-duty pushrods are dropped into position, then the cups are filled with assembly lube before the rockers are installed. With the rocker shaft properly torqued, the engine is rotated in increments and the valve lash is adjusted.

The job of correctly installing the lines, brackets, and accessories takes time, but once it is completed, David maneuvers the turbocharger into place in the valley.

Here is a side-by-side comparison of the stock exhaust manifolds and the PPE High Flow units. With most of the engine reassembled and the turbo in position, installing the exhaust manifolds and up-pipes is the new focus. Once the manifolds are bolted into position, the up-pipes are attached.

Adding the downpipe, coolant tank, air filter, and upper coolant pipe finishes up the Intake Bundle installation.

The last order of business before firing the engine is to top off the fluids. We used a Karen's Transport Duramax Cat oil-filter adapter, which enables us to install a larger Cat filter. Then the engine is filled with Red Line Synthetic Oil 15W-40 diesel engine oil.

A Side-by-Side Comparison of Duramax Heads

We did a visual comparison of the new Edelbrock '11-to-'16 Duramax cylinder heads and stock pieces that were taken off. There are some definite differences in the design of the castings. The extra material in the Edelbrock heads (for custom porting and increased strength) is very noticeable. Take a look at the following images (the Edelbrock are the clean ones).

Behind-the-Wheel Impressions

Since installing the Edelbrock Duramax diesel cylinder heads, Ray has had some time to really drive the '14 GMC Sierra 3500HD and give us some insight into how the engine feels. "As far as the driveability and torque gains, it feels like a completely different truck," he says. "Pulling a trailer seems even more effortless, with less downshifting and lower EGT when going up a grade. The heads even drastically changed the sound of the engine and gave it a lot smoother idle. Overall, I am extremely impressed with the heads."