Banks Sidewinder D-Max Type-R
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are known for their longevity and durability. But entering a Duramax-powered
GMC Sierra in endurance road races against some of the country’s
top sports cars seems completely out of place.
The innovative Banks has already set land speed records with a Cummins-powered Dakota that was driven, not towed, to Bonneville. Now his current project—titled Sidewinder D-Max Type-R—is out to radically change the perception of diesel power on the race track as well as the street.
The truck will compete in 2006 National Auto Sport Assn. series in the Super Unlimited Class, which can include World Challenge and other high-end road-racing cars. Plans had been made to run in the grueling 25 Hours of Thunderhill this weekend (December 4-5), but testing on the just-painted truck wasn’t completed.
A Banks spokesperson said component evaluation was continuing and team owner Gale Banks didn’t want to interrupt the test schedule just to be in the race. According to Banks, endurance testing finds weaknesses in every part and he needs to find and address each one.
The truck will run in the opening test session on the 15-turn, 3-mile Thunderhill course the Friday before the 25-Hour race as part of its evaluation but will not compete this year.
Unlike other diesel projects that focus solely on simply forcing more air and fuel into the cylinders, the Banks team wanted to implement more racing tricks and design innovations throughout the engine. Banks had access to four stock 6.6-liter Duramax LLY engines for testing and development. In another section of the shop, work centered on building a NASCAR-style chassis and fabricating aerodynamically enhanced body panels.
Cylinder block preparation was just as precise as any race engine. The block was rifle-drilled to supply oil to the lifters. Banks CNC milled a billet oil pan for the 7-stage dry-sump system. The custom pan also serves as a block reinforcement girdle. Custom 4340 billet-steel H-beam connecting rods are mated with stock pistons and crankshaft, but both components are heavily modified. The crank was lightened and knife-edged while the pistons were softened in the dome area and an inside lip around the bowl was relieved. The piston crowns were also slightly beveled to allow for expansion under higher exhaust temperatures. Final compression ratio is 14.5:1.
There wasn’t much the engineers could do with the 4-valve cylinder heads. The Banks team cut up donor heads in various cross sections but couldn’t find enough metal to hog out as desired. Some porting was done with a CNC machine to promote swirl, then additional shaping was handled with a hand grinder.
Other head improvements included stainless steel intake and Inconel exhaust valves (both 33mm) and smaller but stronger Eibach springs. The stock 2-piece rocker bridges—those are the pieces that activate 2 rocker arms from a single pushrod—were replaced with custom-machined units. Despite the limitations of the port size, Banks improved air flow by 30 percent on intake side and 50 percent on exhaust.
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