General Motors has an extended historical past of creating modern strides in engine improvement. The Chevrolet small-block V-8, for instance, started life within the Fifties and shortly turned the usual for top horsepower in a small bundle, a legacy that continues into right this moment’s fifth-generation GM V-8s. Even GM’s lineup of V-6 engines made waves all through the business, starting from the 60-degree V-6 that powered practically each GM automobile from 1980 by 2010, to the twin-turbocharged V-6 powering the Cadillac ATS-V.

However, GM has a lesser-known engine household that deserves admiration for its outside-the-box pondering and excellent technological developments, the Atlas engine household. That Atlas household consisted of three principal engines; the front-running 4.2-liter inline-six, the three.5-liter five-cylinder, and the two.8-liter four-cylinder. All three shared the identical primary structure and a variety of elements, although it was the 4.2-liter that led the Atlas program. Here’s a more in-depth take a look at the technical points and historical past of GM’s Atlas 4.2-liter inline six.

In order to provide the most modern and correct data attainable, the info used to compile this text was sourced from numerous producer web sites and different authoritative sources, together with Motor Trend.

Vortec 4200 Technical Specifications

The 4.2-Liter Atlas I-6’s History

To uncover the distinctive particulars of the GM Atlas engine, in any other case referred to as the Vortec 4200, we reached out to GM and located Tom Sutter, the Assistant Chief Engineer for the Atlas. Sutter has been concerned with engine applications for the final 30 years, starting from Oldsmobile’s Quad Four to Cadillac’s present V-Series mills.

Looking Towards Other GM Engines For Inspiration

During improvement, Tom Sutter reverted to his time growing the Oldsmobile Quad Four, GM’s first four-valve per cylinder engine, which was essentially a small-block Chevy inline-six engine. The same design was sketched for the Atlas and finally turned an integral a part of the challenge.

Twin overhead camshafts had been used to regulate the exhaust and consumption valves individually.

Furthermore, GM’s first stab at variable valve timing was put into place on the exhaust aspect. This allowed the GM inline-six engine to breathe deeper throughout high-throttle conditions, leading to larger energy with out the gas consumption penalty being current all through the rev vary. GM’s new modern valve cowl stored issues quiet below the hood, which was constructed utilizing a plastic-like composite materials.

GM even used its comparatively new manufacturing methodology for the Atlas engine block and cylinder head. Called the Lost Foam Casting method, it mainly makes use of a pre-shaped block of Styrofoam buried in sand. Molten aluminum is then poured in, filling the voids left by the melting foam. The result’s an excellent detailed engine block that requires little or no tough machining.

Its Impact On Motorsport

The GM Atlas engine additionally had a short-lived racing profession. General Motors contracted with Falconer, a specialty engine builder, to assemble a 5.0-liter, high-performance model of the Atlas inline-six.

It produced roughly 600 horsepower at 7,500 rpm and 450 pound-feet of torque at 6,000 rpm, however shared virtually no elements with the manufacturing engine.

Herzog Motorsports ran the vans fitted with the GM Atlas inline-six, with the primary race truck being the Vortec Trailblazer that ran in the Baja 500 and Baja 1000 off-road races in 2000. The one-off car was constructed with a tube-frame chassis and coated with a carbon-fiber physique. Driven by Larry Ragland, the 81 Vortec Trailblazer solely competed in these two Baja races, earlier than retiring to Ragland’s storage.

The GM Atlas Engine’s Diverse Potential

The 4.2-liter Atlas engine was a groundbreaking engine for GM. It featured an all-aluminum building, twin overhead cams with variable valve timing on the exhaust aspect, 4 valves per cylinder, a coil-on-plug ignition system, a excessive compression ratio of 10:1, and its cylinder heads featured GM’s then-prevalent “Vortec” engineering designed to maximise airflow.

The 4.2-liter Chevy inline-six was constructed on the GMT360 platform, which was used for SUVs such as the Chevrolet Trailblazer, GMC Envoy, Buick Rainier, Oldsmobile Bravada, Isuzu Ascender, and Saab 9-7X.

Each of those mid-sized SUVs shared the identical cutting-edge structure, together with the business’s first totally hydroformed body in a mid-size SUV. Introduced for the 2002 mannequin 12 months, the GMT360 platform bought a pair million examples worldwide earlier than ending manufacturing after 2009.

Pushing The Industry Forward

GM additionally broke floor within the SUV section by utilizing a twin overhead camshaft with roller-followers to regulate the 4 valves per cylinder. The design was chosen due to the massive quantity of air 4 valves can transfer, whereas the roller-followers supplied a smoother operation with much less friction than typical lifters, including to the engine’s effectivity.

Thanks to the variety of valves, their sizes had been stored small to assist with cooling. Large coolant chambers had been routed across the valves and the center-mounted spark plugs, additional serving to the engine run cooler. Because of the environment friendly cooling and the decreased threat of detonation, the Atlas inline-six was capable of run its excessive compression ratio with out the necessity for premium gas.

The Further In-Depth Craftmanship For The Atlas Inline-Six

As effectively as utilizing twin overhead camshaft, GM’s Atlas inline-six engine featured further components that in the end led to its success. A brand new engine comes with new challenges, resulting in GM introducing all-new elements to extract from its giant fleet of SUVs on the time.

As talked about earlier than, the Vortec 4200 was the primary GM truck engine to characteristic variable valve timing. This early adopter solely had variable valve timing on the exhaust aspect, nonetheless, however allowed for 25 levels of exhaust cam phasing. This stored torque ranges at near-peak ranges all through the rev vary and allowed a higher maximum horsepower with out killing gas effectivity or hindering drivability at decrease RPM ranges.

A First-Of-Its-Kind drive-by-wire System

The Chevy Atlas engine was additionally managed by a drive-by-wire system, one other first in a GM truck software. The system used an digital throttle with no mechanical linkage between the gasoline pedal and the throttle physique, managed by the PCM and was opened through an electrical motor mounted contained in the 77-mm diameter throttle physique.

The modern consumption manifold featured a 180-degree bend, bringing air into the throttle physique simply above the engine and wrapping it round into the cross-flow cylinder head.

The consumption manifold was stored brief with the intention to accommodate easy accessibility to the spark plugs, including a much-welcomed contact of practicality.

Its Unique Mounting System

The GM Atlas inline-six additionally utilized an modern mounting system for its equipment. Each part moreover the ability steering pump was mounted on to the block. This consists of the alternator, A/C compressor, and loafer pulley. GM says this helped eradicate play within the belt-drive system since every part was completely positioned in relation to the block.

Key Takeaways:

• The General Motors Atlas inline-six engine was first launched in 2002, getting used for autos such because the Chevrolet Trailblazer and GMC Envoy.
• The Atlas engine was utilized in off-road race vans, which competing in iconic races such because the Baja 1000.
• Smaller variations of the Atlas engines had been launched after the I-6’s success, together with the Vortec 3500 and the Vortec 2800.
• Production of the GM Atlas engine resulted in 2009, as a result of dimension and prices of the engine not being a logical enterprise choice transferring ahead.

The End of an Era

The Vortec 4200 was an enormous leap ahead for GM powertrains. But regardless of this, the modern inline-six didn’t take pleasure in an extended life. It was the cancelation of the GMT360 platform in 2009 that spelled the tip for the Vortec 4200.

The engine merely wouldn’t slot in different purposes. “The length of the engine and its structure definitely played a part in that,” Sutter mentioned. “The engine doesn’t work in a transverse application, so it was limited in the vehicle choices.”

The inline-six would theoretically have slot in GM’s full-size vans just like the Chevrolet Silverado and GMC Sierra. However, it was logistics that prevented that from taking place. Those vans used GM’s 4.3-liter V-6 as their base engine, which was based on the GM small-block V-8.

What Were The Other Atlas Engines?

Two years after the Atlas inline-six, GM launched a smaller Atlas engine, named the Vortec 3500. Instead of six cylinders, the Vortec 3500 decreased the scale right down to solely 5, with a displacement of three.5 liters. It used the identical 3.7-inch cylinder bore and 4.0-inch piston stroke because the Vortec 4200, together with the identical rods, pistons, and valves.

The Vortec 3500 was utilized in GM’s compact pickups, these being the first-generation Chevrolet Colorado and GMC Canyon. Both vans had been launched for the 2004 mannequin 12 months and used the five-cylinder because the extra-cost engine possibility over the Vortec 2800 four-cylinder. The straight-five produced 220 horsepower and 225 pound-feet of torque.

Speaking of the Vortec 2800 engine, this four-cylinder Atlas engine additionally used lots of the similar elements, together with the rods, pistons and valves. A giant cause for this was to maintain prices in examine, but additionally helped entice prospects after the success of the Atlas I-6 engine. Standard for the Chevrolet Colorado and the GMC Canyon, the Vortec 2800 would produce 175 horsepower and 185 pound-feet of torque.

Despite having a reasonably brief lifespan of solely seven years, the GM Atlas engine, notably the primary inline-six iteration, set the stage for additional improvements below the hood of numerous vehicles and vans. Despite not being as spoken about as engines reminiscent of Chevrolet’s big-block V-8s or the LS7 Crate engines, the Atlas’ contributions to the business cannot be forgotten.