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LS7 Unplugged

Here's an inside look at the biggest, baddest small-block ever built by GM

lthough it's built on the same Gen III/Gen IV architecture as the current LS1 and LS2 engines, the 7.0-liter LS7 that comes as standard equipment in the '06 Corvette Z06 can't really be compared with them.

No, the 427-cube, 500hp, all-aluminum power plant more closely matches up with the legendary big-blocks of the musclecar heyday. While speculation has raged for years regarding the actual output of Chevy's baddest big-blocks, the new LS7 now ranks right up there with them as one of the most powerful engines ever offered by Chevrolet. Did the 1970 LS6 really make just 450 hp? And what about the supposed 475 horses of the ZL1?

Chew on these stats for a moment:
*The bore is 4.125 inches and the stroke is 4.000 inches*CNC-ported aluminum heads have 12-degree valve angles--just like the American Le Mans racing Corvettes
*The intake valves and connecting rods are titanium
*The camshaft delivers 0.591-inch of lift and 230/211 degrees of duration at 0.050
*The dry-sump oiling system is connected to an 8-quart reservoir mounted in the engine compartment
*This is, after all, the engine of a street-legal production car, but a rollcage and a set of Comp T/A R-1 tires are all the car needs to be a full-fledged track competitor.

Just as interesting as the LS7's specifi-cations is its assembly process at the new GM Performance Build Center (PBC), in the industrial 'burbs of Detroit. A single technician builds each engine by hand. It's a process that marches 180 degrees away from GM's typical mass-production methods.

The V-8 plant at St. Catharines, Ontario, for example, will produce thousands of engines in a day; the PBC might build 100. Indeed, it's a more intimate procedure, with a small, hand-selected group of experienced enthusiasts performing the assembly duties.

We toured the facility recently to watch--and help with--the assembly of an LS7 engine. At 100,000 square feet (and not all of it currently utilized), the PBC's shop floor is downright miniscule compared to other GM large-scale manufacturing operations. While we've been through other GM plants, and were surprised by the cleanliness and brightness of the assembly area, the PBC ratchets those qualities up several notches. It's more like the setting of a high-end Indy car or NASCAR race shop.

You'll see the LS7's build process unfold in the accompanying photos, but here's a quick rundown of the overall assembly procedure: Each engine is hand-assembled by a single technician who builds it from start to finish. (There's even a plaque with the builder's name affixed to the engine after the final inspections are completed.) He or she starts with a bare, cleaned block and begins the build by installing bearings--just like you would on an at-home build.

Yes, there are some power tools involved, most notably computer-monitored torque "wrenches" that provide far more accuracy and repeatability than conventional handtools could offer in a production line setting, but all the procedures are performed by the technician. He or she taps each rod-and-piston assembly into its respective bore and installs each main bearing one at a time. There are 13 build stations in a U-shape line. The technician has approximately 23 minutes to complete the task(s) prescribed for said station. There is a guide at each station that directs the builder to the tasks, the order they're to be performed, and even the sequence in which the fasteners should be tightened. A bar code reader at each station acts as the electronic checklist, recording the tasks performed, as well as every, single fastener's torque reading.

During our time on the line, we also learned a few more tidbits about the LS7, like the fact that Mobil 1 synthetic oil is the only lube used in the assembly, from the cam, to bearings, to any other part that needs assembly lubrication. It's stored at each build station in ketchup bottles.

After each engine is assembled and inspected, it is pushed to a balance station where it runs briefly on natural gas during a two-step balancing procedure. From the balance station, the engines are shipped to Johnson Matthey Testing in Taylor, Michigan, where they're subjected to a 20-minute "hot" test--10 minutes of no-load "break in" and 10 minutes of loaded operation. After this, the engines come back to the PBC and are ready to ship to the Corvette assembly facility in Bowling Green, Kentucky.

Frankly, we were amazed at the process because it seems so, well, un-GM. It's encouraging that even the General and his enormous mass production army can adjust the standard operating procedure when needed.

GM has suffered in the market and media this year, but the Z06 and, particularly, its hand-built LS7 engine, are examples of things gone right. Really right.

LS7: The Crate Engine You've Been Waiting For

The folks at GM Performance Parts were on hand at our LS7 assembly line tour to tell us the 500-horse engine will be available as a crate engine right about the time the Corvette Z06 goes into production.

The crate engine package won't include the complete dry-sump oiling system, but it will likely be offered separately. A number of aftermarket systems should work, too, although the factory supply and scavenge outlets don't have conventional or AN-type fittings.

No, it won't be cheap, but then again, this is a hand-built, 500-horse engine with CNC-ported heads, and a whole mess of exotic materials. It sounds perfect for, say, a '70 Corvette or maybe a Pro Touring Chevy II. Don't be surprised to see other Z06 items in the next GMPP catalog too.

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