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GM’s LS V-10 Lives!

The prototype Gen III/IV-based V-10 is being rebuilt and fitted with twin-turbos.

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Yes, you read that right. As far back as 1994 GM was toying with the idea of building a V-10. Mopar and Ford each had one, so it should come as no surprise that GM would be interested in doing an engineering study on it. Instead of spending money to continually upgrade the big-block V-8 and make it comply with emissions, a V-10 that was based off the same platform as an existing V-8 had many advantages. From a performance perspective, a 10 cylinder also has advantages—thanks to an increase in piston area (at the same displacement)—that could help push the platform to new heights. Had it come to fruition, there would have been an iron truck block version and an aluminum Corvette version.

The proposed GM V-10 was essentially a Gen III LS engine with two extra cylinders, a 90-degree block with uneven-firing cylinders like the Mopar V-10. According to a GM High-Tech Performance story by David Vizard (“Perfect 10”), GM spent $310,000 on prototype tooling for two iron blocks that were ordered and “still floating around the bowels of Powertrain Advanced Engineering in Pontiac, MI.” With so many changes over the years, including the newly opened Global Powertrain Engineering Center built at the same location, some of these old relics have a tendency to walk out the door. This brings us to today. The folks at VC Fabrication in Kansas City, Kansas, have one of these engines in their possession, which was recently rebuilt with new pistons. Check out this video of the crank being balanced.

02 GM V10 Stillborn Prototype 2/24

Lee Masters at VC Fabrication says this engine was said to be in an Escalade before it was tossed in the trash. We can probably assume that this engine was not one of the original Gen III V-10s, though, because it has DOD (Displacement on Demand – cylinder deactivation on the passenger bank that turns the V-10 into an inline 5-cylinder for fuel mileage) and VVT (variable valve timing) like the Gen IV engines as well as an LS3/L92-style rectangular [intake] port and [D-port exhaust] head. Both of which did not exist until much later than 1994. The Gen III V-10 supposedly used an LS6 style, cathedral port head. According to Lee’s research on the date codes, the engine dates to 2004. It has a total of four knock sensors, located on the sides of the block, and a 58x reluctor wheel. The firing order is 1-8-7-6-5-4-3-10-9-2, an even fire at 72-degrees.

03 GM V10 Stillborn Prototype 3/24
04 GM V10 Stillborn Prototype 4/24

A 4.00-inch bore and 3.622-inch stroke puts displacement around 455 cubic-inches (7.5-liters), as was originally proposed. This was further verified by the 7.5/7.7 stamping on the head gaskets. Perhaps there was a 4.065-inch bore version in the works as well? The crankshaft uses an 8-bolt flange like the LSA (but not the same) to handle the extra torque going to the flexplate. Lee says the camshaft measures 24.875-inches in length, rides on six journal bearings, and has .478-inch lift (gross). The intake manifold and valley cover are also unique to the V-10. The intake manifold uses twin electronic throttle bodies with no crossover between banks. The oil pan resembles the all-wheel-drive GM truck’s V-8 as does the front accessory drive, which supports the theory that it was previously used in an Escalade to explore its use in the truck market.

VC Fabrication chose to delete VVT and DOD with some Texas Speed sourced parts and dropped this engine in a 1964 Impala 2-door hardtop. Under a tight deadline to make the World of Wheels show, the crew fabricated valve covers, intake manifold and headers using flanges from ICT Billet, who also made a custom valley cover. The headers may be used to feed a custom twin-turbo system in the future, built in-house. A custom wiring harness and Megasquirt EFI will be the final touches to get this beast running with a 4L80E 4-speed to handle the power. Project Stillborn, as they call it, made the Kansas City World of Wheels show just in time, and is nearing its first start-up.

Lee Masters of VC Fabrication credits the help of Logan Sell, Ryan Mitchell and his crew for pulling this project together in a short amount of time.

07 GM V10 Stillborn Prototype 5/24
09 GM V10 Stillborn Prototype 1964 Impala 6/24
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