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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.

GM will recall 3.5 million pickups and SUVs to fix brake issue

WASHINGTON — General Motors Co is recalling 3.46 million U.S. pickup trucks and SUVs to address a vacuum pump issue that could make braking more difficult and increase the risk of a crash. The recall, which covers 2014-2018 model year vehicles, including some Cadillac Escalade, Chevrolet Silverado, Chevrolet Tahoe, GMC Sierra, Chevrolet Suburban and GMC Yukon vehicles, was triggered because the amount of vacuum created by the vacuum pump may decrease over time, GM told the National Highway Traffic Safety Administration (NHTSA) in documents posted Wednesday. NHTSA opened a preliminary investigation into the issue in November 2018, and said it had reports of 9 crashes and two injuries related to the issue. It provided GM in July with additional field reports that prompted the automaker to open an investigation. The company did not immediately say on Wednesday how many injuries or crashes are linked to the issue but said it could impact braking in "rare circumstances." GM said dealers will reprogram the Electronic Brake Control Module with a new calibration that will improve how the system utilizes the hydraulic brake boost assist function when vacuum assist is depleted. GM said the vacuum assist pump, which is lubricated with engine oil that flows into the pump through a filter screen, can in some cases lose effectiveness over time, as debris such as oil sludge can accumulate on the filter screen. GM told NHTSA that prior model years used a different brake assist system design, and vehicles manufactured after 2018 were not equipped with the affected pump design. Recalls Chevrolet GM GMC

Car and Driver reveals spy shots of mid-engine 2017 Corvette

Some news in the car world is perennial, and some is perennially wrong. Typically news about some upcoming mid-engined Chevy Corvette has fallen into the latter category, with rumors never yet generating a road car. This time could very well be different. Car and Driver has some exclusive photographs of what would appear to be a Corvette test mule with a mid-mounted engine. The car in question might look like a Holden SSV ute that's undergone some indelicate modification, but C/D editor Don Sherman assures that the bones of a C8 'Vette live within that crude bodywork. Sherman points to the closeness of the cabin to the front axle as clue number one of this car's mid-engine attitude, as well as the powertrain-sized space between the back of the seats and the rear axle. The roof and glasshouse are all clearly plucked from the current C7, and the gas tank filler positioned on the B-pillar is another huge clue. The buff book estimates that the mule points to a timeline for sale, even. Testing on this level could mean a mid-engined C8 ready for sale in as few as 20 months, or for the 2017 model year. Click over to Car and Driver to have a close look at this important set of spy photographs, as well as a rendering of what a finished C8 might ultimately look like