I didn't know the GM Atlas engine was a thing

"medumdum" (medumdum) 08/17/2020 at 09:28 • Filed to: Atlas I-6, technical, gm, engine swaps, engines

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These look kinda drab, but hide a gem of an engine!

The GM V8 is the undisputed king of engine swaps. 2JZ/1JZ and Honda swaps are pretty common, but nothing captivates the minds of hot rodders quite like the 350 small block and the LS series of engines; however behind the big name LS, GM also has a really solid straight six that I didn’t know was a thing until this weekend, when I was looking through online classifieds (as we do) and clicked on a 04 Trailblazer and noticed the seller described the engine as a straight six. I thought it was the same as the V4 engines people list their Accords and Neons with, but it was not!

It was used mostly in the Colorado and Trailblazer, or anything else based on the GMT360 platform. I had always just assumed these trucks used an inline 4 and a V6 as engine choices, like the GMT325 that the S10 was based on, but this is not the case! The Atlas was the engine line developed by GM for this pla . Mark McNabb wrote !!!error: Indecipherable SUB-paragraph formatting!!! , but here’s some highlights.

The LL8 was the big daddy of the range, with 4.2L of displacement upon introduction in the 2002 Trailblazer. From the LL8, four- and five-cylinder derivatives were made, which are just as interesting, but for now let’s focus on the sexy six.

Featuring an all-aluminum design, DOHC, and variable valve timing, it showcased the engineering brilliance of the same company that built the ubiquitous small blocks and LS that are the top picks for engine swaps. One of the main things that interested me in the engine was the juxtaposition of old and new in the engineering of it. It GMs first foray into variable valve timing and allowed them to avoid using an exhaust gas recirculation system and still meet emissions requirements. The removal of EGR systems is a very common mod done by tuners and does provide several performance benefits.

Goodbye EGR!

In an EGR system, gases from the exhaust are sent back into the intake in order to reduce toxic engine emissions. However, these gases also dilute the air going into the engine. For performance, you always want as much clean air going into your intake, and exhaust is not clean air.

That VVT system, along with a healthy 10.0 compression ratio, allowed GM to crank 270hp out of the engine, while still recommending regular fuel. These were solid numbers for the time, and are still not bad!

Sadly, the Atlas engine didn’t stick around. After the GMT360 platform, GM switched to unibody construction and FWD transverse layouts. I4s and V6s were better suited to these tasks, and GM really didn’t have another application for the engine. A base model Silverado or Camaro with a straight 6 instead of a V6 would be very interesting for turbo applications, but wouldn’t make sense from a manufacturer’s standpoint

Nobody buying a new SUV is going to care why or how their car moves, they just want it to move for a couple years until they buy the new one. Because of this, there was no successor to the sweet straight six that GM had blessed us with.

The real reason I’m interested in this engine, is of course swap ideas. Straight sixes like the Ford Barra and the 2JZ are legendary for being able to take massive abuse from turbos, and the LL8 is no exception. Attach a big’ol snail to any of these bad boys and you’ll have a fast machine; however good lucking finding a cheap 2JZ or Barra anywhere outside of Australia. The Barra and the 2JZ are also iron block engines, which is good for taking boost but not so much for weight. Theoretically, the all-aluminum LL8 won’t be able to take as much abuse due to the weaker metal, but it will be a lot lighter.

The main issue with the LL8 currently is aftermarket support. While there is some, it isn’t nearly as prevalent as stuff for LS or 2JZ swaps. I hope more people find out about this engine and start modding it, because I’d certainly like more options for future projects. Since it was used in mass-market vehicles, junkyards have these engines at the ready and can be found for dirt cheap. A lighter and cheaper alternative to a 2JZ that sounds like an overall win-win in my book!

gmporschenut also a fan of hondas > medumdum 08/17/2020 at 22:44

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My mom had one. It was a good engine with a shit car around it. 

medumdum > gmporschenut also a fan of hondas 08/18/2020 at 08:52

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Hey that’s fine by me, makes them all the cheaper!

Who is the Leader - 404 / Blog No Longer Available > gmporschenut also a fan of hondas 08/18/2020 at 09:54

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This basically sums up my feelings about the GMT360s. Though I still really like the way the Trailblazer’s tallights blended into the bumper scuff panel when the plastic wasn’t horribly faded.

I’ve always wondered why that engine wasn’t used more.