Urban Legend Verified: KC Maxx Rebuilding GM Prototype LS V10

As an online publication dedicated to late model GM performance, with a specific focus on the LS and LT engine platforms we hear all manner of rumors at LSX Magazine. Rumors, legends, and lore, of engines that never were, top secret programs that were squirreled away somewhere by a few rogue engineers but never saw the actual light of day. The auto industry has been filled with these stories almost since its beginning.

In recent years we’ve seen a number of variations of the LS platform. Those include the recent 16 cylinder engine developed and built by Steve Morris for a super car manufacturer, which uses some LS architecture to achieve staggering horsepower numbers. As cool as that engine is, it’s not cost-effective or practical for the majority of our readers, or anywhere near the realm of what they may pursue.

The engine is similar to the LS7 but with two more cylinders and a different bore. Images courtesy KC Maxx Performance and VC Fabrication.

Today, we’re going to add to the list of urban legend and lore surrounding the LS, with this engine recently brought to our attention by Lee Masters over at KC Maxx Performance and VC Fabrication in Kansas City, Kansas. The guys over at KC Maxx recently acquired this engine, that as far as we were told or knew up until this week, had never actually existed. A V10 LS.

The V10 crankshaft (left) next to a typical LS crankshaft (right).

We had heard of this engine from the source we acquired it from, when I saw it, I knew we had to get our hands on it. Eventually it became available and we acquired it from the supplier who purchased it from GM. -Lee Masters

We’d heard and even read about a secret program back in the mid 1990s to bring a V10 to the GM engine lineup. Some intrepid GM engineers it seemed, thought that the General needed a V10 to replace the aging 454 in the truck division. Having such an engine available could also be used to develop a possible candidate for the Corvette or other GM supercar. Additionally, the V10 would in theory have similar displacement with more power, while only being slightly larger in length than the big block 454, and more easily adaptable to modern and future emissions standards and GM technologies. We were told however, that this project never got off the ground to make it past the modeling and CADD stages.

Fast forward nearly 20 years later and it appears that GM in some capacity whether official or otherwise did research and prototype a LS based V10 engine, possibly just over a decade ago. The engine you see before you was sold as scrap and spare parts to a buyer with an assorted lot of other pieces unrelated to it. The engine was missing an exhaust manifold, and had a damaged valve cover, but was otherwise complete from intake manifold to oil pan. “We had heard of this engine from the source we acquired it from, when I saw it, I knew we had to get our hands on it. Eventually it became available and we acquired it from the supplier who purchased it from GM,” says Masters.

According to Masters, KC Maxx acquired the engine recently, and since the shop specializes in late model GM performance the shop crew decided to revive the engine and make it the center piece of a ’64 Impala project for the upcoming Kansas City World of Wheels show in February.

We talked at length with Masters regarding this peculiar engine, which he says KC Maxx has torn down and is having machined and prepped for a complete rebuild. The LSV10 appears to be based around the late model LS engine architecture sharing much of its key characteristics with the LS2 and LS7.

The block uses the 4.00-inch bore shared with several LS family engines and the also LS familiar 3.70-inch stroke. Displacement comes in at 465 cubic-inches or 7.6-liters.

The block utilizes a 4.00-inch bore which is shared with the LS2, LQ4, LQ9, LY6, L76 and 4.00-inch stroke found in the LS7. This puts displacement with 10 cylinders around 455 cubic-inches (7.5-liters).The pistons have reliefs cut in them similar to the OEM design of the LS2, and the shop estimates that the engine should have a compression ratio between 9.8-10.2:1. The crankshaft uses the LSA/CTS-V 8-bolt flex-plate.

Of course, a one-off camshaft would have been developed and used for this application as well. The cam that was pulled from this engine measures 24.875-inches in length and rides on six bearing journals. Gross lift of the camshaft has been measured at .478-inch, however duration is unknown. The camshaft also utilizes GM’s single bolt variable valve timing actuator. Currently the firing order is unknown, the KC Maxx team hopes to have that sorted prior to installing an electronic control system once the engine is reassembled.

The cylinder heads utilize LS7 D-shaped ports.

Masters says that the engine also contains provisions for GM’s displacement on demand (DOD). “It appears that this engine could shut-down half its cylinders, completely shutting off one side. This would allow it to run as an inline five-cylinder when the displacement on demand system kicked in.”

According to Masters the cylinder head port configuration is identical to the D-shaped ports of an LS7 save for the extra cylinder at each end. Masters says the valvetrain utilizes L92 rocker arms and lifters and the rocker stands are CNC machined. Interestingly the cylinder head gaskets, while they may be one off are stamped 7.5/7.7, as if GM or one of its suppliers had at least gone through the trouble to create tooling to manufacture and even stamp these gaskets like all other OEM LS engine series gaskets. Also curious is the 7.7 in that stamping. That may also indicate that GM had plans for a slightly larger displacement variant of this engine as well, possibly using a longer stroke.

Rocker arms come from the LQ9, and the rocker stands are CNC machined.

Four knock sensors are located where we’d expect them on any LS engine. The KC Maxx team has found one crankshaft position sensor, although they suspect the design likely utilized two. A custom valley cover was necessary for this application, although a cursory glance could almost mistake it for a typical LS valley cover.

The valley cover is a custom part, but is very similar to a V8 LS valley cover.

The intake manifold uses twin throttle bodies with no cross-over.

The intake manifold is an interesting piece. In our research regarding the LS V10 that never made it past a few CAD drawings and foam models that engine appeared to wear a low-profile intake manifold similar to what is found on most passenger car LS engines (Corvette, Camaro, G8, etc). This engine however uses what appears to be a unique manifold. The twin throttle-body design feeds each bank individually. Masters says there is no cross-over within the manifold. This would further aide a displacement on demand system in shutting down one bank of the engine completely, including airflow for anything other than cooling purposes, possibly further improving on performance, emissions, and efficiency when running in DOD mode.

Masters says the rear engine cover is similar if not identical to that of an LS3 engine. The front covers while similar to the LS3 design are unique themselves. The engine however, does utilize a typical LS3-equipped GM truck front engine accessory drive, and was equipped with such when it arrived at KC Maxx, including a LY6 style water pump.

The oil pan is also familiar in appearance. Masters says that it resembles an all wheel drive or four wheel drive GM truck oil pan. That makes sense according to what else Masters says he was told about the engine from his source at GM.

“According to our research on the serial numbers stamped in the parts on this engine, this engine would have been built around 2004. All the pieces are stamped with a part or engineering numbers similar to anything else that would come through on the production line.

Left: The oil pan is similar to a GM four-wheel drive or all-wheel drive pan. Right: The engine came with a GM truck front engine accessory drive and is also set up for LSA/CTS-V eight-bolt flex-plate.

Our GM sources says that around the time of this engine’s development, GM was looking to get into the V10 market to compete with the Ford pickup V10 and even the Dodge SRT-10 pickup. This engine we are told made 616 horsepower and 789 lb-ft of torque.

“Our GM sources says that around the time of this engine’s development, GM was looking to get into the V10 market to compete with the Ford pickup V10 and even the Dodge SRT-10 pickup. This engine we are told made 616 horsepower and 789 lb-ft of torque.”
Masters says that KC Maxx will be installing this engine into a ’64 Impala Two Door for the Kansas City World of Wheels Show. That car he says was nothing special like an SS or special package, and when KC Maxx acquired it, was already set up for an LS3 swap.

Custom headers and valve cover flanges are being outsourced so that KC Maxx can fabricate replacements for custom exhaust and valve covers. Masters says that the shop is also looking into a fabricating a custom intake manifold rather than the bulky, and rather ugly OEM prototype part.

The KC Maxx crew is currently looking into what engine management system to run on this application. Masters says the shop is leaning towards a Holley Dominator EFI setup, but nothing has been confirmed yet.

The World of Wheels show is not the last stop for this project. The engine will be tuned and dyno’d at KC Maxx in OEM style configuration. Masters says plans are also in the works to possibly add a twin turbo system, which could potentially boost power into the four-digit range with every little effort. “Obviously the twin throttle body configuration would lend itself well to a unique twin turbo setup,” Masters says.

We’ll be curious to see what this engine pulls on the chassis dyno once KC Maxx has it sorted, and follow its progression. Once in a great while one of these urban legend engines sees the light of day, we’re just glad someone is actually doing something with it rather than putting it on a stand and under glass for display in a museum or auction house. You can follow the progress of the build and the car at the KC Maxx and VC Fabrication Facebook pages as well.

About the author

Don Creason

Don Creason is an automotive journalist with passions that lie from everything classic, all the way to modern muscle. Experienced tech writer, and all around car aficionado, Don's love for both cars and writing makes him the perfect addition to the Power Automedia team of experts.
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