Corvette Engine Selection - Project C4orce Update

Project C4orce Started Out As A Fairly Normal Magazine Project, But It's Grown Into Something Much More Than That. A Host Of Engine Selections Is Just The Beginning

Dave Emanuel Apr 10, 2009 0 Comment(s)
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If you've been paying attention, you've probably noticed that coverage of Project C4orce has been blatantly absent for quite a few months. Ye of little faith have undoubtedly concluded that the project has been abandoned, sold by aliens, or worse. In fact, it has suffered the fate of so many long-term projects-unforeseen problems and scheduling conflicts that inevitably lead into a series of stalls, detours, and U-turns.

Part of the problem is that the project took on a life of its own. The original concept was to produce a high-tech C4 for less than $15,000. We're still on track to do that, but as the project has progressed, feedback from readers and project sponsors made it apparent that Project C4orce needed a special appearance in addition to special performance.

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A 5.3L engine similar to this one began life beneath the hood of a Silverado pickup. For the past year, it has been living happily beneath the hood of the '87 Corvette known as Project C4orce. In addition to replacing the truck intake manifold with one from an LS6, we also treated the engine to a set of ported heads and a special C4orce camshaft.

Another aspect of the project's evolution is a need to expand the C4orce concept of documented and registered vehicles to cover C5s and C6s. Consequently, we've been developing components and packages that will apply to '97-and-later Corvettes. The accompanying matrix shows the engine combinations that will be found under the C4orce umbrella and will be available for purchase very soon.

It starts with the 5.3L LS-series engines originally installed in trucks, SUVs, and late-model Impalas. These engines, which are available with cast-iron and aluminum blocks, are relatively easy to find at reasonable prices (especially those with cast-iron blocks). As you may remember, we paid $700 for a complete 5.3L engine (including starter, alternator, A/C compressor, PCM, and harness) for Project C4orce. This wasn't a one-time deal. Johnson Thomas, who works with us on some projects, purchased an almost identical engine for the same price and is installing it in an '88 Third-Gen Camaro.

Since there's no substitute for cubic inches, (or cubic centimeters, if you're metrically predisposed) and to accommodate owners of C5s and C6s, we decided to put together a selection of C4orce engines, based on original bore/stroke configurations. Since all LS-series engines, except the 4.8L truck engine and the LS7, have the same stroke (3.622 inches) that's obviously the dimension to use for all engines that incorporate a stock crankshaft. If you're going to use an aftermarket crank, the logical stroke dimension is 4.00 inches. It's sufficiently longer than the stock stroke to put a bulge in the torque curve and is coincidentally the same length as the crank in LS7 engines.

Overall displacement specifications will vary to some degree depending on finished cylinder bore diameter, but the C4orce standard engine package specifications are based on commonly used reference dimensions. Engines and rotating assemblies with other bore/stroke dimensions will be available on a special-order basis.

One of the advantages of standardizing bore/stroke combinations is enhanced availability and parts interchangeability. As an example, if you find a great deal on a 5.3 engine and decide to build it with a 4.00-inch stroke, you'll wind up with 6 liters. If you subsequently decide that bigger really is better and acquire a block with a 3.900-, 4.000-, or 4.060-inch bore, you can pull the rotating assembly out of the 5.3, order the appropriate pistons, and reuse the existing crankshaft and connecting rods. Since the C4orce connecting rods and 4-inch crankshaft rods are the same, regardless of the block in which they're to be installed, these components should never be out of stock.

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This LS1 engine, installed in an '01 C5 has been given the C4orce treatment, which includes ported LS6 cylinder heads, a ported throttle body, a C4orce camshaft, and C4orce special tuning. It produces 449 hp at the wheels, idles at 800 rpm, and can be driven at 1,000 rpm in Sixth gear with the original 3.42:1 rear gears still in place.

C4orce engine packages tremendously expand choices for C4 owners and also provide a number of options for C5 and C6 owners by offering combinations for virtually all popular LS-series production blocks. That makes it easy to put an engine together with parts already in hand, rather than making it a necessity to use only newly purchased components. One of the few major components that may lead to a state of confusion is the crankshaft. Although the forgings are physically identical, if an engine is to be controlled by an LS1-style PCM, a crankshaft with a 24-tooth reluctor must be used. If an E38 or E40 ECM is going to be calling the shots, a 58-tooth reluctor is necessary.

As is the case with all C4orce components, all engines are designed to deliver great value. One example is the 417ci LS3 combination. While its horsepower potential is somewhat lower than that of an LS7, its costs are significantly lower. An LS3 block and a pair of assembled cylinder heads cost approximately the same amount as a bare LS7 block. With a reasonably mild camshaft, initial testing indicates our 417ci LS3-based engine should put out 525-550 hp at the wheels.

We've also developed a stock-displacement LS1/LS6 combination that puts out 450 hp at the wheels, and a really mild 5.3L package that produces 330 hp at the wheels (for reference, a stock 5.3 engine typically cranks out 250-260 hp). A more aggressive 5.3L package, like the one that's installed in Project C4orce, produces about 375 rwhp.

With all of these engine combinations, our focus has been on combining efficiency and reliability with a broad powerband. While this might not deliver the numbers necessary to win "can you top this" contests, it will deliver engines that produce power curves that optimize driving fun, and the ability to demonstrate that when it comes to horsepower, sometimes less is more-as in less at the top end and more in the middle equals better overall performance.

The C4orce engine matrix is a work in progress, so it will be changing and expanding over the next few months. In addition to partial and complete engines, we'll also be adding a variety of individual components and assemblies to the C4orce program. Look for periodic updates in future issues of Corvette Fever.

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