We had to find out more. The owner is Darrin Gartrell of LS Brackets from Woodward, Oklahoma. Darrin confirmed it is a legitimate GM LS with 10 slugs in the block. In the long history of GM skunkworks and back-office science projects, it appears this was one of those projects that somehow made it out the back door. No one outside of GM really knows how many were made or how many actually made it into the wild. However, this is believed to be the first one running in a vehicle, and it has a pretty cool story to boot.

It turns out sometime around 2008, amid GM’s financial woes, they scuttered a large number of projects. Everything was sold off as scrap and slated for destruction. Some enterprising individuals recognized this gem sitting among the junk as something unique and worth saving. The whole pile was purchased and loaded on the spot before it could escape. After not being seen again for several years, the engine finally surfaced and Darrin bought it.

The prototype LS V-10 engine finally met up with someone who could give it life. Upon first seeing the engine, he noticed it needed some TLC and was missing several parts before it could run. After the initial teardown, Darrin got in touch with several knowledgeable people in the automotive performance industry and let them know what he had and wanted to do with it.

While several articles were written about these elusive V-10 engines, no one really knew much about them or their design. Darrin had plans to add power, so he sent the cam off to Billy Godbold at Comp Cams to study and make blanks for the inevitable upgrades. Once he was done, John Bewley at Full Proof Performance worked his magic, spec’ing out the cam upgrade. Meanwhile, the factory crank was sent off to be studied and reverse engineered. Darrin shipped the cylinder heads (which resemble a factory L92 head in port design) off to Gavin Simcoe for some much-needed inspection and cleanup.

Amid all this, what started as a one-off engine build morphed into Darrin forming the LS XR10 group with the ultimate goal of producing a brand-new V-10 based on the original GM design, so the prototype became a testbed for future models. COVID-19 slowed the process of assembling all the parts back at LS Brackets/LS XR10 headquarters.

Darrin entrusted Michael Rudd at Rudd Racing Engines in Lone Grove, Oklahoma, to perform final assembly and dyno tuning. The prototype is a cast-iron Gen IV-style block with a 4-inch bore and 3.622 stroke crankshaft. After a slight cleanup, the final bore comes to 4.005 inches for a total of 456 ci. The factory crankshaft and Gen IV rods reside inside with upgraded CP-Carrillo pistons to end up with an 11.2:1 compression ratio.

While the engine came with the factory prototype dual throttle-body intake, it lacked in the upper-rpm range. It was also less than aesthetically pleasing, so Darrin cut down two Edelbrock Pro-Flo XT intakes to make one with 10 runners running a MaxxECU PRO system. Swiftek Engineering in Australia got the nod to design the custom valve covers and valley cover. Meanwhile, Chris Stewart of Stewy’s Speed Shop in Oklahoma welded those beautiful custom headers. Rick Gorski with FireCore Performance provided the excellent FireCore50 wires for this build. A Holley mid-mount accessory drive runs all the ancillaries.

Once Rudd assembled the engine, Scott Clark with Real Tuners was on hand for the first true start of the engine outside of a GM facility. After some initial break-in, diagnostics, and Clark nailing down the tune, it was ready for its first full-power run. Silent for 10 years, the V-10 finally ran again (and stronger than ever at full song), rocking the dyno with 700 hp at 7,000 rpm and 615 lb-ft of torque at 4,800 rpm. If you wonder what an LS-based V-10 engine would sound like at 7,000 rpm, Darrin says it is a beautiful sound all its own.

That engine now sits between the framerails of this ’55 Chevy, which started out with a good-running and driving 454ci four-speed combo. It now sports a Nerd Rods Chassis 2×4-inch boxed frame with a full-custom crossmember and control arms with QA1 coilovers and 14-inch Wilwood brakes on C4 Corvette spindles all the way around. The power is transferred through a 3,500-stall Circle D Billet torque converter to a GM 4L85E transmission. A Currie TrueTrac 9-inch with a 3.70:1 gear ratio is triangulated at the rear.

Darrin did all the sheetmetal work before sending it to Covington’s Customs in Woodward, Oklahoma, for bodywork and a slathering of PPG red and black paint. Schott Throttle wheels and Michelin Pilot Sport 4 S tires (325/30R19 rear, 245/40R18 front) look right at home on the ’55. The car debuted at the Tri-Five Nationals, where it rightfully earned a Top 25 award.

Now that it’s finished, Darrin plans to drive the car as much as possible. He builds them to drive them and there is no doubt it is one heck of a calling card for his V-10 production plans. He is now busy putting together all the puzzle pieces and is hoping to have it in production by mid 2023 so that you, too, can have a super-rare, unique engine with a sound all its own!