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2014 Chevrolet Silverado and GMC Sierra debut all-new designs, three new engines

General Motors has finally dropped the curtain on the 2014 Chevrolet Silverado and 2014 GMC Sierra. Both trucks have undergone substantial revisions with updated versions of the company's 4.3-liter V6, 5.3-liter V8 and 6.2-liter V8 engines. In a shot across the bows of both Ford and Chrysler, GM says it won't use a V6 engine adapted from passenger car applications. Instead, it developed the 4.3-liter engine based on its proven truck-duty architecture.
All three mills will boast direct injection fuel systems as well as a new cylinder head design. Combined with a revised piston, the new engines feature a smaller combustion chamber with a compression ratio of 11:1 or higher depending on the application. Cylinder deactivation and continuously variable valve timing are all part of the recipe, and each engine is paired with a six-speed automatic transmission with auto grade breaking. So far, no fuel economy or horsepower figures have been released, though GM says the new engines will best their predecessors in both areas.
Outside, the trucks feature a number of enhancements to reduce drag and wind noise, and GM claims both the Silverado and Sierra will offer buyers some of the quietest cabins in the class. Extended cab models now feature front-hinged rear doors to allow easier access to the back passenger area, and Crew Cab buyers can now select between a five-foot, eight-inch bed or a six-foot, six-inch bed. Buyers with a mind toward going off road will also rejoice in the return of the Z71 package, complete with Rancho shocks, front tow hooks and additional under-body protection.

Mopar Hellephant is sold out, but here are 4 other awesome crate V8s to try

Despite a relatively enormous $30,000 price tag, Mopar's 1,000-horsepower supercharged Hellephant crate engine sold out in just 48 hours. Some enthusiasts may have missed out on the crazy engine due to lack of funds, or they just assumed there would still be some Hellephants down the line. But worry not, swap-happy gearheads. There are plenty of V8s in the world to pick from, and we highlighted four favorites. They're not as powerful, but they're all cheaper, and still have a lot to offer. Mopar 6.2L Hellcrate Odds are a lot of prospective Hellephant buyers were Mopar fans to begin with, so we'll start the list with the next-most-potent offering: the Hellcrate. This is the same supercharged 6.2-liter V8 found under the hood of the Dodge Charger and Challenger Hellcats and the Grand Cherokee Trackhawk. It makes 707 horsepower and 650 pound-feet of torque like those cars, too. It's also about $10,000 cheaper than the Hellephant engine at $20,020, and that leftover money can be used to finish the project or for aftermarket upgrades to get it closer to the Hellephant's output. GM LS9 6.2L The Hellcrate isn't the only factory supercharged crate engine on the market. From General Motors comes the supercharged 6.2-liter LS9 V8. This is the engine that was used in the C6 Corvette ZR1. At 638 horsepower and 604 pound-feet of torque, it doesn't make as much power or torque as the Hellcrate. But it does boast a dry sump oil system. So instead of pumping oil out of a pan at the bottom, the engine uses an oil tank mounted remotely that pumps oil into the engine. This means the engine is shorter overall, and can be mounted lower for a better center of gravity. It also means that there's almost no risk of running the engine dry in hard cornering, as could happen with a normal oil sump where the oil can slosh to the side without the oil pump. Basically, it offers some major benefits if you want supercharged V8 power for a road course car. It's also a tad cheaper than the Hellcrate at $18,149. But get one while you can, because GM is only selling what's left from when it was building the C6 ZR1. Ford Aluminator 5.2XS Our pick from the Blue Oval lacks a supercharger, but it's still pretty sweet.

Watch this week's Top Gear America used-car challenge

Top Gear America is back for the penultimate episode of the first season. Used car challenges were some of the highlights of the original UK edition. In our exclusive clip, Tom Ford, Antron Brown and William Fichtner run their $7,000 sports cars in a drag race. As expected, the trio chose very different cars for the challenge. Watch the video to see if a Subaru WRX's all-wheel drive can overcome a power deficit to beat a Ford Mustang and a Chevy Corvette. Brown and Fichtner also spend some time relaxing with an old Jeep Wagoneer. Like them, we're really hoping Jeep will bring back the Wagoneer nameplate. Brown also drives a Maserati Levante, proving that not all family cars need be boring. This week's guest star is actor, rapper and former host of Pimp My Ride, Xzibit. Top Gear America airs Sundays at 8 p.m. Eastern on BBC America. Related Video: Celebrities TV/Movies Chevrolet Ford Subaru Top Gear exclusive top gear america