Is This the Biggest Displacement LS Engine Ever?

The argument for Big Block Chevy V8 has always been one of size. “I have more cubic inches than you” is the usual selling point that we are told. We are curious as to how they would respond when confronted with this LS engine.

Let’s say it aloud: five-hundred and twenty-three cubic inches of displacement. This 523 c.i. (8.6L) LSX engine is the result of modifying the deck to give extra stroke, without compromising piston or crank integrity. Built by RHS (Racing Head Service) it features a hydraulic roller cam, and 11.5:1 compression pistons. Interestingly, the biggest available engine package RHS advertises is an 810 horsepower/502 c.i. engine. This is likely a one-off build done at the customer’s request.

From there Houston House of Power/Chuck’s Tuning dyno tuned the engine on E85 and the result is 701 wheel horsepower and 647 lb-ft of torque, all motor baby! From what can be made out, the curve looks a bit soft below 3,000RPM, which is surprising considering the displacement, but that may be an intention tuning device used to prevent knock if the engine gets too loaded up at low RPM. Quoting RHS on their 502 c.i.-based package, the operating range of the motor is 2,500-6,500RPM, and I’m guessing this 523 is similar. Apparently the drivability is top notch considering the engine is making 700 naturally-aspirated wheel horsepower. With the tuner chiming in that the setup could easily make more if they wanted to go all out. That’s the benefit of massive cubes, I suppose.

Perhaps I’m just that level of twisted, but I wonder how well a 523 cubic inch air pump would respond to a little bit of laughing gas? I’m guessing a 50 shot would go a long way with an engine this big. Just thinking out loud here… Anyway, what are your thoughts: is 523 cubes the limit of an LSX engine or have you built something crazier?

Jake Stumph is the Content Editor behind LS1tech.com. He is an avid racer and car enthusiast. He considers himself very lucky to be able to write about cars. You can follow him on Facebook and YouTube.

Jake Stumph

Jake Stumph is a lifelong car enthusiast and racer, and former content editor for Internet Brands Automotive which he joined in 2015. His work has been featured by several other prominent automotive outlets, including Jalopnik and Autobytel.

He obtained a bachelor's degree in Political Science at the Ohio State University in 2013, then pivoted from covering politics and policy to writing about his automotive adventures, something that, he says, is a lot more fun. Since that time, he has established connections with most of the world's major automakers, as well as other key brands in the automotive industry.

He enjoys track days, drifting, and autocross, at least, when his cars are running right, which is uncommon.

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