The Atlas engines feature aluminum cylinder blocks and heads, with the cylinder bores featuring replaceable steel cylinder liners.[1] The 4- and 5-cylinder versions feature dual balance shafts,[3][4] balance shafts being unnecessary in the 6-cylinder.[5]
The Atlas program began in 1995 along with the planning for GM's next-generation mid-size SUVs and pickup trucks. These vehicles were designed around the I6 engine. The I6 version was used in a Baja 1000 racing truck, winning its first race in a class that also included V8 engines. Another I6-powered truck won the truck class at the Pikes Peak International Hillclimb.
It displaces 4.2 L (4,160 cc; 253.9 cu in), with a 93 mm × 102 mm (3.66 in × 4.02 in) bore and stroke. It has four valves per cylinder, utilizes dual-overhead cams (DOHC) design, and features variable valve timing on the exhaust cam, a first for GM inline engines. When introduced, this engine's power was 270 hp (201 kW) at 6,000 rpm and torque was 275 lb⋅ft (373 N⋅m) at 3,600 rpm. 2003 saw a slight bump in power to 275 hp (205 kW), while torque was unchanged. For 2006, power was increased to 291 hp (217 kW) at 6,000 rpm and torque to 277 lb⋅ft (376 N⋅m)) at 4800 rpm with the addition of a MAF and a complete internal redesign of the engine; however, due to the new SAE rating procedures, ratings can vary slightly between years. The engine redline is 6,300 rpm. The LL8 was on the Ward's 10 Best Engines list for 2002 through 2005 and was the basis for all the other Atlas engines. With the closure of the Moraine, Ohio, plant and the discontinuation of the GMT360 platform (Chevrolet TrailBlazer, GMC Envoy, etc.), production of the LL8 also ended.[6]
The LLR (also called Vortec 3700), is a straight-5DOHC engine produced from 2007 through 2012. It displaces 3.7 L; 222.9 cu in (3,653 cc), courtesy of a larger 95.5 mm (3.76 in) bore while keeping the 102 mm (4.02 in) stroke. The LLR also corrected the head issue found in the L52. It produces 242 hp (180 kW) at 5,600 rpm and 242 lb⋅ft (328 N⋅m) at 4,600 rpm. The engine redline is 6,300 rpm.[6] This five-cylinder engine achieves better fuel economy and performance than the six-cylinder, but with more power and torque than the four-cylinder.[1]
The L52 (also called Vortec 3500), is a straight-5DOHC engine produced from 2004 through 2006. It displaces 3.5 L; 211.1 cu in (3,460 cc), with a 93 mm × 102 mm (3.66 in × 4.02 in) bore and stroke. Dynoed at the flywheel it produces 220 hp (164 kW) at 5,600 rpm and 225 lb⋅ft (305 N⋅m) at 2,800 rpm. The engine redline is 6,300 rpm.[4]
The LLV (also called Vortec 2900) is a 2.9 L; 178.3 cu in (2,921 cc) straight-4DOHC engine produced between 2007 and 2012, with a 95.5 mm × 102 mm (3.76 in × 4.02 in) bore and a stroke. It replaced the LK5 and produced 185 hp (138 kW) at 5,600 rpm and 190 lb⋅ft (258 N⋅m) of torque at 2,800 rpm. The engine redline is 6,300 rpm.[7]
The LK5 (also called the Vortec 2800) is a 2.8 L; 169.0 cu in (2,770 cc) straight-4DOHC engine produced between 2004 and 2006, with a 93 mm × 102 mm (3.66 in × 4.02 in) bore and stroke. It produces 175 hp (130 kW) at 5,600 rpm and 185 lb⋅ft (251 N⋅m) of torque at 2,800 rpm. The engine redline is 6,300 rpm.[3]
_engine_in_2006_Chevrolet_Trailblazer.jpg)
