Banks Big Head
More Boost for the LB7 Duramax 6600

---

By Jim Bigley

---

Banks has a Big Head - wastegate actuator that is. The key ingredients to more turbodiesel power are more fuel and higher boost pressures. A naturally aspirated engine runs at one atmosphere of air pressure, or about 14.7-psia (absolute) at sea level. Double that with approximately 15-psig (gauge), and you're effectively doubling engine displacement. Raise boost further to say 30-psig along with the right amount of diesel fuel, and (assuming effective intercooling) you now have a Duramax with power equivalent to a 19.8L diesel engine. This is big power! The Banks Big Head incorporates an adjustable turbo wastegate linkage, allowing you to raise boost pressure to get that power increase.

The Big Head gets its name from having a larger internal pressure diaphragm and spring, theoretically improving operation. This produces a larger diameter can, which makes a great spot for a Banks Big Head sticker.

The early prototype engines came with an adjustable wastegate actuator, as seen in the Ron Wong photo of a Duramax 6600 display engine. The Chevy and GMC prototypes we tested here in Montana during the fall of 1999 also came with adjustable wastegate actuators. Those of you handy with tools could probably modify a stock piece - making it adjustable - but the relatively low cost of the Banks Big Head reduces the DIY incentive.

The 4-page instruction sheet includes a couple of line drawings to aid in component identification, and the instructions are, in typical Banks fashion, easy to read and understand. Banks offers a Technical Service Hotline at 1-888-839-2700, and any installation questions you might have will be answered by their knowledgeable staff 7:00 am - 5:00 pm (Pacific Time), though I doubt most Duramax owners will need help with this kit.

Once the engine cover has been removed, you can remove the three bolts securing the turbo heat shield. These three bolts require a 10mm socket. Once the bolts have been removed, just tip the heat shield up and back against the firewall.

You'll need a T55 Torx bit to remove the upper coolant fitting on the turbocharger. This has to be removed to allow access to the top actuator bracket bolt (bracket bolts require a 12mm socket or end-wrench). I bought the T55 Torx bit shown here at NAPA (#775-5971). We used a ¼" plastic pipe plug to plug the coolant hole in the turbo, once the Torx fitting had been removed. If you loosen the coolant surge tank pressure cap to relieve pressure, and work quickly, you may lose only a cup or two of coolant once the Torx fitting has been removed and replaced with the plastic plug. This coolant fitting is at a high point in the cooling system, so there's not a lot of gravity feed.

I should mention that you'll be laying on or leaning over the engine to gain access to the turbo area. Be extra careful not to put weight on the air conditioning hoses and lines. Breaking an aluminum A/C line could double or triple the cost of installing the Big Head. Secondly, working at the back of the engine can be a little awkward. Be very deliberate in removing and re-installing the hardware. Murphy's Law dictates that a dropped bolt or tool will disappear into the most inaccessible location. If you've got butterfingers, don't begin this installation without a mechanic's stick magnet.

I recommend removing the actuator head from the bracket by first removing the two lock-nuts on the back side. It'll be easier to bolt the bracket onto the turbo without the head and rod getting in the way, and you'll be able to more accurately adjust the actuator rod once you get to that step in the instructions.

The Banks instructions indicate that once the rod length has been adjusted so the rod pin can be inserted into the wastegate arm with the wastegate closed, disconnect the rod, then turn the rod 5 full turns - making the rod shorter. This is the preload set point. Getting the shorter rod length reconnected to the wastegate arm on the turbo requires that you use air pressure, applied to the Banks Big Head, to extend the actuator rod. I used about 40-psi. This portion of the installation is made easier if the head is loose on the bracket.

In an earlier Big Head installation I participated in, the 5 turns allowed the turbocharger to produce about 22-psi boost pressure. This is just slightly above or equal to stock boost pressure. I used 6 turns for this installation, which produced about 26-psi. I may need another turn to reach my goal of 30-psi for our Duramax Hot-Rod Project. You may need to vary the wastegate rod length adjustment to produce the boost pressure you're looking for. Stock boost pressures for the LB7 Duramax 6600 can vary between 18 and 22-psi.

Some have recommended boost pressures approaching 35-psi. However, this is getting uncomfortably close to the spooky 39-psi level, where reports have indicated serious turbo overspeed occurs, resulting in disintegration of either the compressor or turbine wheel. You don't want to go there...

In addition to the Big Head, Banks produces a complete performance "package" for the Duramax. The downside to the complete Banks package is both cost (about $1900) and installation time (a local installer told me it took two of them approximately 8 hours for their first Banks installation). It is a complex kit to install, but does provide an enviable level of quality, performance and value.     TDP

Banks retailer: