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Chevy's 6.6-liter Duramax is pretty much all new

To say there's a heated battle in heavy-duty pickups is an understatement, with Chevrolet, Ford, and Ram constantly trading blows of increased torque, horsepower, and towing capacity. The latest salvo is the revised, more powerful turbo diesel 6.6-liter Duramax V8 in the 2017 Chevy Silverado. It has 910 pound-feet of torque, an increase of 145, putting it nearly level with the Ford Super Duty. Here's a closer look at where those gains come from. How exactly did Chevrolet add all that torque plus 48 horsepower? The automaker essentially took a fine-tooth comb to the entire engine. Chevy says it changed 90 percent of the V8, and the cumulative effect of those small changes adds up to big increases. As you might guess, the turbocharger is updated. The larger unit features electric actuation of the variable nozzle turbine (VNT), and what Chevy calls a double axle cartridge mechanism that separates the VNT moving parts from the housing. That helps with heat performance as well, with a claim that the exhaust side of the turbo can run continuously up to 1,436 degrees Fahrenheit. Helping that cause are six exhaust gaskets made of Inconel - an nickel alloy that contains chromium and iron – and upgraded stainless steel for the exhaust manifold. Despite having the same cast iron cylinder block, albeit with some minor enhancements, the engine has new cylinder heads, pistons, piston pins, connecting rods, and crankshaft, which have all been upgraded to handle 20 percent higher cylinder pressures. Alongside the increase in pressure, Chevrolet also increased the cylinder head's structure with a honeycomb design. The pattern features high-strength aluminum with dual layer water jackets that not only improve strength, but also optimize water flow for better cooling. For 2017, the cylinder head also benefits from integrated plenum that aids the engine in getting more air under heavy loads. The cylinder head isn't the only component to get a minor update, as the pistons have a larger diameter pin for improved oil flow. The same detailed improvements has been bestowed to the humble connecting rods (second in our hearts only to the inanimate carbon rod). The new design has the bolts oriented roughly 45-degrees to the rod instead of parallel. The angle split design, as it's called allows for easier passage through the cylinder.

2014 Chevy Silverado High Country spied wearing trappings of new luxury trim

Spy photographers have spotted the new Chevrolet Silverado High Country and GMC Sierra Denali out on public streets for a little testing. From the looks of things, the Silverado will receive a much-differentiated front fascia along with special badges and those honking 20-inch chrome wheels. Expect to find a more posh interior as well. Likewise, the Sierra Denali will wear a tweaked nose with the familiar Denali bling. The one of the GMC trucks spotted here rolls on 21-inch gunmetal wheels instead of the 20-inch chrome pieces of the High Country.
Word has it both trucks will go on sale after the Texas State Fair this summer. While General Motors hasn't said for certain what we can expect to find under the hood, we'd be surprised to see anything outside of the range of engines found in the standard Silverado and Sierra models. That means buyers should be able to get their hands on the efficient, 23-miles per gallon 5.3-liter V8.

GMC Yukon spy shots show refresh with Acadia-style interior

GMC seems to be moving quickly to get its line-up's interiors all on the same page. These spy photos reveal that the GMC Yukon full-size SUV line will be getting an update that will refresh the exterior somewhat, and the interior much more significantly. The design of the interior is clearly derived that of the new Acadia. The center stack is dominated by one large vertical touchscreen, and sitting in the lower quarter of the screen is a floating multifunction knob. At the base of the screen are some chunky piano-key style buttons. They appear to be connected to some of the climate functions based on the screen's readout. On either side of the screen are vertical air vents, and we can just make out a bit of wood trim. Much of the rest of the dash is still hidden, but it's pretty clear this interior will look very close to that of the Acadia, as the screen and vent layout looks nearly identical. That means there should be an instrument cowl that extends just far enough to meet the center screen, and the rest of the dash should be fairly simple and unadorned. One other note, the steering wheel in this test vehicle has the lights and sensors for Super Cruise, so that will likely be offered, too. As for the exterior of the new Yukon, it won't be radically changed. While the Acadia and Terrain will be nearly all-new, the Yukon will just be a refresh with changes focused on the front and rear fascias. They're still very well covered in these spy shots, but expect some changes to grille shape and headlights to change somewhat. The example pictured appears to be an AT4 trim based on the shortened front bumper for improved approach angle. It also seems likely that the next AT4 will adopt the signature amber fender marker lights from the HD trucks, Canyon and now Acadia. Since this is a refresh, we wouldn't be surprised if we see the new Yukon shown sometime this year or early next. It will probably continue to offer the same range of engines and transmissions, including both gas V8s and the diesel inline-6. Related Video