The LS swap. In the world of custom automotive builds, few phrases evoke such levels of excitement or contempt. The GM-built V8 engine is exceedingly popular thanks to its compact design, reliability, affordability, and ability to produce big horsepower. That’s why you see it in everything from Chevy Camaro restomods to street rods, and yes, it even crosses the forbidden line to power Ford Mustang builds and all kinds of import projects. If you really want to see LS contempt, show up to a Mazda rotary meet with an LS-swapped RX7.

What if you want an LS experience without the V8 rumble? Enter Race Cast Engineering, an Australian-based company that loves the LS engine but also has a serious mad-scientist vibe going. The team has tinkered with a V12 version of the big-block LSX mill for a few years now, and it’s ready to go pro as a 750-horsepower (559-kilowatt) naturally aspired crate engine. If you haven’t already done so, hit the video above to hear the sheer lunacy of this massive 9.5-liter (yes, 9.5-liter) monster in action, both on a dyno and stuffed into a Kia van. Seriously, we weren’t kidding about the whole mad scientist thing.

Gallery: V12 LS Engine

Allow us a few moments to get technical, because the details of this mill are interesting even for those who don’t speak the LS language. This is obviously a custom single-piece build as opposed to a V8 with four extra cylinders welded into place. That said, the iron block is very true to the 7.0-liter LSX engine with the same 4.125-inch cylinder bore. However, to make it a bit more rev-happy, Race Cast uses the shorter 3.62-inch stroke found on smaller-displacement LS engines. It runs a surprisingly mild camshaft (single cam in the block), and at full throttle, this massive mill still spins to 7,100 RPM. It also idles surprisingly smooth below 900 RPM, making it shockingly streetable.

The dyno shows a maximum of 755 horsepower hitting at 6,500 rpm, but perhaps more impressive is the torque curve. Actually, it’s not really a curve – more than 600 pound-feet (814 Newton-meters) is available at pretty much any rpm, resulting in tire-shredding thrust at the mere thought of touching the throttle. And according to the video, this is the base engine with a safe tune. Going with a hotter cam and more aggressive tuning can yield over 1,000 hp.

The big V12 LS engine hails from Australia, but it will make its North American debut at the 2019 SEMA show in a new Factory Five Racing project. Per the company’s website, it’s available to order right now, but as you’d expect, it’s not cheap. A turn-key engine lists for $55,200, but for builders seeking something truly unique with capability for big power, this could be the ultimate LS swap.

Got a tip for us? Email: